Sample records for black holes

This article deals with two questions, namely whether it is possible for blackholes to exist, and if the answer is yes, whether we have found any yet. In deciding whether blackholes can exist or not the central role in the shaping of our universe played by the forse of gravity is discussed, and in deciding whether we are likely to find blackholes in the universe the author looks at the way stars evolve, as well as white dwarfs and neutron stars. He also discusses the problem how to detect a blackhole, possible blackholes, a southern blackhole, massive blackholes, as well as why blackholes are studied

Following an introductory section, the subject is discussed under the headings: on the character of research in blackhole astrophysics; isolated holes produced by collapse of normal stars; blackholes in binary systems; blackholes in globular clusters; blackholes in quasars and active galactic nuclei; primordial blackholes; concluding remarks on the present state of research in blackhole astrophysics. (U.K.)

Written by foremost experts, this short book gives a clear description of the physics of quantum blackholes. The reader will learn about quantum blackholes in four and higher dimensions, primordial blackholes, the production of blackholes in high energy particle collisions, Hawking radiation, blackholes in models of low scale quantum gravity and quantum gravitational aspects of blackholes.

In years 1920 as a result of quantum mechanics principles governing the structure of ordinary matter, a sudden importance for a problem raised a long time ago by Laplace: what happens when a massive body becomes so dense that even light cannot escape from its gravitational field. It is difficult to conceive how could be avoided in the actual universe the accumulation of important masses of cold matter having been submitted to gravitational breaking down followed by the formation of what is called to day a blackhole [fr

Conditions for the formation of a blackhole are considered, and the properties of blackholes. The possibility of Cygnus X-1 as a blackhole is discussed. Einstein's theory of general relativity in relation to the formation of blackholes is discussed. (U.K.)

Methods and results of searching for stellar mass blackholes in binary systems and for supermassive blackholes in galactic nuclei of different types are described. As of now (June 2002), a total of 100 blackhole candidates are known. All the necessary conditions Einstein's General Relativity imposes on the observational properties of blackholes are satisfied for candidate objects available, thus further assuring the existence of blackholes in the Universe. Prospects for obtaining sufficient criteria for reliably distinguishing candidate blackholes from real blackholes are discussed. (reviews of topical problems)

Macroscopic entropy of an extremal blackhole is expected to be determined completely by its near horizon geometry. Thus two blackholes with identical near horizon geometries should have identical macroscopic entropy, and the expected equality between macroscopic and microscopic entropies will then imply that they have identical degeneracies of microstates. An apparent counterexample is provided by the 4D-5D lift relating BMPV blackhole to a four dimensional blackhole. The two blackholes have identical near horizon geometries but different microscopic spectrum. We suggest that this discrepancy can be accounted for by blackhole hair - degrees of freedom living outside the horizon and contributing to the degeneracies. We identify these degrees of freedom for both the four and the five dimensional blackholes and show that after their contributions are removed from the microscopic degeneracies of the respective systems, the result for the four and five dimensional blackholes match exactly.

This is a review of current theory of black-hole dynamics, concentrating on the framework in terms of trapping horizons. Summaries are given of the history, the classical theory of blackholes, the defining ideas of dynamical blackholes, the basic laws, conservation laws for energy and angular momentum, other physical quantities and the limit of local equilibrium. Some new material concerns how processes such as black-hole evaporation and coalescence might be described by a single trapping h...

Recent work, which has been investigating the use of the concept of entropy with respect to gravitating systems, blackholes and the universe as a whole, is discussed. The resulting theory of blackholes assigns a finite temperature to them -about 10 -7 K for ordinary blackholes of stellar mass -which is in complete agreement with thermodynamical concepts. It is also shown that blackholes must continuously emit particles just like ordinary bodies which have a certain temperature. (U.K.)

Charged blackhole solutions with pion hair are discussed. These can be\\ud used to study monopole blackhole catalysis of proton decay.\\ud There also exist\\ud multi-blackhole skyrmion solutions with BPS monopole behaviour.

First page Back Continue Last page Overview Graphics. What is blackhole? Possible end phase of a star: A star is a massive, luminous ball of plasma having continuous nuclear burning. Star exhausts nuclear fuel →. White Dwarf, Neutron Star, BlackHole. Blackhole's gravitational field is so powerful that even ...

We study the problem of spatially stabilizing four dimensional extremal blackholes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing blackholes placed in external fields we find that taking a continuum limit of Denef et al.'s multicenter supersymmetric blackhole solutions provides a supergravity description of such backgrounds within which a blackhole can be trapped within a confined volume. This construction is realized by solving for a levitating blackhole over a magnetic dipole base. We comment on how such a construction is akin to a mechanical levitron.

We revisit the geometry representing l collinear Schwarzschild blackholes. It is seen that the blackholes' horizons are deformed by their mutual gravitational attraction. The geometry has a string like conical singularity that connects the holes but has nevertheless a well defined action. Using standard gravitational thermodynamics techniques we determine the free energy for two blackholes at fixed temperature and distance, their entropy and mutual force. When the blackholes are far apart the results agree with Newtonian gravity expectations. This analyses is generalized to the case of charged blackholes. Then we consider blackholes embedded in string/M-theory as bound states of branes. Using the effective string description of these bound states and for large separation we reproduce exactly the semi-classical result for the entropy, including the correction associated with the interaction between the holes

We investigate isolated white holes surrounded by vacuum, which correspond to the time reversal of eternal blackholes that do not evaporate. We show that isolated white holes produce quasi-thermal Hawking radiation. The time reversal of this radiation, incident on a blackhole precursor, constitutes a special preparation that will cause the blackhole to become eternal. (paper)

Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical blackholes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of blackhole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized blackholes observed in the Milky Way, the formation and evolution of supermassive blackholes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of blackholes supporting theoretical understanding of the coalescence of blackholes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.

It is shown that there are large static blackholes for which all curvature invariants are small near the event horizon, yet any object which falls in experiences enormous tidal forces outside the horizon. These blackholes are charged and near extremality, and exist in a wide class of theories including string theory. The implications for cosmic censorship and the blackhole information puzzle are discussed. copyright 1997 The American Physical Society

We construct a four-dimensional BPS saturated heterotic string solution from the Taub-NUT solution. It is a nonextremal blackhole solution since its Euler number is nonzero. We evaluate its blackhole entropy semiclassically. We discuss the relation between the blackhole entropy and the degeneracy of string states. The entropy of our string solution can be understood as the microscopic entropy which counts the elementary string states without any complications. copyright 1997 The American Physical Society

Applying Einstein's theory of gravitation to blackholes and their interactions with their surroundings leads to the conclusion that the sum of the surface areas of several blackholes can never become less. This is shown to be analogous to entropy in thermodynamics, and the term entropy is also thus applied to blackholes. Continuing, expressions are found for the temperature of a blackhole and its luminosity. Thermal radiation is shown to lead to explosion of the blackhole. Numerical examples are discussed involving the temperature, the mass, the luminosity and the lifetime of black mini-holes. It is pointed out that no explosions corresponding to the prediction have been observed. It is also shown that the principle of conservation of leptons and baryons is broken by hot blackholes, but that this need not be a problem. The related concept of instantons is cited. It is thought that understanding of thermal radiation from blackholes may be important for the development of a quantified gravitation theory. (JIW)

Supersymmetric blackholes are characterized by a large number of degenerate ground states. We argue that these blackholes, like other quantum mechanical systems with such a degeneracy, are subject to a phenomenon which is called the geometric or Berry’s phase: under adiabatic variations of the

Review essay, Marcia Bartusiak, BlackHole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015).......Review essay, Marcia Bartusiak, BlackHole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015)....

Jan 27, 2016 ... In the following paper, certain blackhole dynamic potentials have been developed definitively on the lines of classical thermodynamics. These potentials have been refined in view of the small differences in the equations of the laws of blackhole dynamics as given by Bekenstein and those of ...

I find a class of blackhole solutions to a (3+1) dimensional theory gravity coupled to abelian gauge fields with negative cosmological constant that has been proposed as the dual theory to a Lifshitz theory describing critical phenomena in (2+1) dimensions. These blackholes are all asymptotic to a Lifshitz fixed point geometry and depend on a single parameter that determines both their area (or size) and their charge. Most of the solutions are obtained numerically, but an exact solution is also obtained for a particular value of this parameter. The thermodynamic behaviour of large blackholes is almost the same regardless of genus, but differs considerably for small blackholes. Screening behaviour is exhibited in the dual theory for any genus, but the critical length at which it sets in is genus-dependent for small blackholes.

as a star or dispersing altogether. Were we engineers with advanced technology, we might attempt to find that critical amount of energy necessary to form a blackhole. However, despite some fears to the contrary, such technology does not exist, so instead we investigate this critical regime numerically. The first step is to pick ...

denotes the partial derivatives of . The construction of a numerical method with which ... which configurations form blackholes and which disperse (the only two options in this model). The problem in picturing such a space is that it is infinite ..... 4.1 The future: Less symmetry. The work described above all assumes spherical ...

Although supermassive blackholes (SMBHs) correlate well with their host galaxies, there is an emerging view that outliers exist. Henize 2-10, NGC 4889, and NGC 1277 are examples of SMBHs at least an order of magnitude more massive than their host galaxy suggests. The dynamical effects of such ultramassive central blackholes is unclear. Here, we perform direct N-body simulations of mergers of galactic nuclei where one blackhole is ultramassive to study the evolution of the remnant and the blackhole dynamics in this extreme regime. We find that the merger remnant is axisymmetric near the center, while near the large SMBH influence radius, the galaxy is triaxial. The SMBH separation shrinks rapidly due to dynamical friction, and quickly forms a binary blackhole; if we scale our model to the most massive estimate for the NGC 1277 blackhole, for example, the timescale for the SMBH separation to shrink from nearly a kiloparsec to less than a parsec is roughly 10 Myr. By the time the SMBHs form a hard binary, gravitational wave emission dominates, and the blackholes coalesce in a mere few Myr. Curiously, these extremely massive binaries appear to nearly bypass the three-body scattering evolutionary phase. Our study suggests that in this extreme case, SMBH coalescence is governed by dynamical friction followed nearly directly by gravitational wave emission, resulting in a rapid and efficient SMBH coalescence timescale. We discuss the implications for gravitational wave event rates and hypervelocity star production

Blackholes, once just fascinating theoretical predictions of how gravity warps space-time according to Einstein's theory, are now generally accepted as astrophysical realities, formed by post-supernova collapse, or as supermassive blackholes mysteriously found at the cores of most galaxies, powering active galactic nuclei, the most powerful objects in the universe. Theoretical understanding has progressed in recent decades with a wider realization that local concepts should characterize blackholes, rather than the global concepts found in textbooks. In particular, notions such as trapping h

In the presence of a complex scalar field scalar–tensor theory allows for scalarized rotating hairy blackholes. We exhibit the domain of existence for these scalarized blackholes, which is bounded by scalarized rotating boson stars and hairy blackholes of General Relativity. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

discusses the cosmology theory of a blackhole, a region where an object loses its identity, but mass, charge, and momentum are conserved. Include are three possible formation processes, theorized properties, and three way they might eventually be detected. (DS)

A new solution of Einstein equation in general relativity is found. This solution solves an outstanding problem of thermodynamics and blackhole physics. Also this work appears to conclude the interpretation of NUT spacetime. (author)

Two-dimensional shadows formed by illuminating vortices are shown to be visually analogous to the gravitational action of blackholes on light and surrounding matter. They could be useful teaching aids demonstrating some of the consequences of general relativity.

We present new AdS4 blackhole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric blackholes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of blackhole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large blackhole phase transition and we interpret the process in the dual field theory.

Full Text Available We review the present status of blackhole thermodynamics. Our review includes discussion of classical blackhole thermodynamics, Hawking radiation from blackholes, the generalized second law, and the issue of entropy bounds. A brief survey also is given of approaches to the calculation of blackhole entropy. We conclude with a discussion of some unresolved open issues.

No particle theory can be complete without gravity. Einstein's theory of gravity is of the Euler-Lagrange form, but standard quantization procedure fails. In quantum gravity the higher order interactions have a dimensionality different form the fundamental ones, because Newton's constant G has dimensions and the renormalization procedure fails. Another problem with quantum gravity is even more mysterious. Suppose that we had regularized the gravitational forces at the small distance end in the way that the weak intermediate vector boson regularized the fundamental 4-fermion interaction vertex of the weak interactions. Then what we discover is that the gravitational forces are unstable. Given sufficiently large amount of matter, it can collapse under its own weight. Classical general relativity tells us what will happen: a blackhole is formed. But how is this formulated in quantum theory. S. Hawking observed that when a field theory is quantized in the background metric of a blackhole, the blackhole actually emits particles in a completely random thermal way. Apparently blackholes are just another form of matter unstable against Hawking decay. Unfortunately this picture cannot be complete. The problem is that the quantum version of blackholes has infinite phase space, and other symptoms of a run-away solution. Blackholes are the heaviest and most compact forms of matter that can be imagined. A complete particle theory can have nothing but a spectrum of black-hole like objects at it high-energy end. This is why it is believed that a resolution of the blackhole problem will in time disclose the complete small-distance structure of our world. 6 references

Scientists using NASA's Swift satellite say they have found newborn blackholes, just seconds old, in a confused state of existence. The holes are consuming material falling into them while somehow propelling other material away at great speeds. "First comes a blast of gamma rays followed by intense pulses of x-rays. The energies involved are much…

We consider an Abelian gauge field coupled to a particular truncation of Horndeski theory. The Galileon field has translation symmetry and couples non minimally both to the metric and the gauge field. When the gauge-scalar coupling is zero the gauge field reduces to a standard Maxwell field. By taking into account the symmetries of the action, we construct charged blackhole solutions. Allowing the scalar field to softly break symmetries of spacetime we construct blackholes where the scalar field is regular on the blackhole event horizon. Some of these solutions can be interpreted as the equivalent of Reissner-Nordstrom blackholes of scalar tensor theories with a non trivial scalar field. A self tuning blackhole solution found previously is extended to the presence of dyonic charge without affecting whatsoever the self tuning of a large positive cosmological constant. Finally, for a general shift invariant scalar tensor theory we demonstrate that the scalar field Ansatz and method we employ are mathematically compatible with the field equations. This opens up the possibility for novel searches of hairy blackholes in a far more general setting of Horndeski theory

Belief in the existence of blackholes is the ultimate act of faith for a physicist. First suggested by the English clergyman John Michell in the year 1784, the gravitational pull of a blackhole is so strong that nothing - not even light - can escape. Gravity might be the weakest of the fundamental forces but black-hole physics is not for the faint-hearted. Blackholes present obvious problems for would-be observers because they cannot, by definition, be seen with conventional telescopes - although before the end of the decade gravitational-wave detectors should be able to study collisions between blackholes. Until then astronomers can only infer the existence of a blackhole from its gravitational influence on other matter, or from the X-rays emitted by gas and dust as they are dragged into the blackhole. However, once this material passes through the 'event horizon' that surrounds the blackhole, we will never see it again - not even with X-ray specs. Despite these observational problems, most physicists and astronomers believe that blackholes do exist. Small blackholes a few kilometres across are thought to form when stars weighing more than about two solar masses collapse under the weight of their own gravity, while supermassive blackholes weighing millions of solar masses appear to be present at the centre of most galaxies. Moreover, some brave physicists have proposed ways to make blackholes - or at least event horizons - in the laboratory. The basic idea behind these 'artificial blackholes' is not to compress a large amount of mass into a small volume, but to reduce the speed of light in a moving medium to less than the speed of the medium and so create an event horizon. The parallels with real blackholes are not exact but the experiments could shed new light on a variety of phenomena. The first challenge, however, is to get money for the research. One year on from a high-profile meeting on artificial blackholes in London, for

The final merger of two blackholes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as future. space-based detectors. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. For many years, numerical codes designed to simulate blackhole mergers were plagued by a host of instabilities. However, recent breakthroughs have conquered these instabilities and opened up this field dramatically. This talk will focus on.the resulting 'gold rush' of new results that is revealing the dynamics and waveforms of binary blackhole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics

The Hawking-Penrose singularity theorem states that a singularity forms inside a blackhole in general relativity. To remove this singularity one must resort to a more fundamental theory. Using a corrected dynamical equation arising in loop quantum cosmology and braneworld models, we study the gravitational collapse of a perfect fluid sphere with a rather general equation of state. In the frame of an observer comoving with this fluid, the sphere pulsates between a maximum and a minimum size, avoiding the singularity. The exterior geometry is also constructed. There are usually an outer and an inner apparent horizon, resembling the Reissner-Nordström situation. For a distant observer the horizon crossing occurs in an infinite time and the pulsations of the blackhole quantum "beating heart" are completely unobservable. However, it may be observable if the blackhole is not spherical symmetric and radiates gravitational wave due to the quadrupole moment, if any.

We demonstrate that rapidly spinning blackholes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical blackholes and predicts observable signatures in blackhole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids.

Blackholes are difficult to study because they emit no light. To overcome this obstacle, scientists are trying to recreate a blackhole in the laboratory. The article gives an overview of the theories of Einstein and Hawking as they pertain to the construction of the Large Hadron Collider (LHC) near Geneva, Switzerland, scheduled for completion in 2006. The LHC will create two beams of protons traveling in opposing directions that will collide and create a plethora of scattered elementary particles. Protons traveling in opposite directions at very high velocities may create particles that come close enough to each other to feel their compacted higher dimensions and create a mega force of gravity that can create tiny laboratory-sized blackholes for fractions of a second. The experiments carried out with LHC will be used to test modern string theory and relativity.

Blackhole gravitohydromagnetics (GHM) is developed from the rudiments to the frontiers of research in this book. GHM describes plasma interactions that combine the effects of gravity and a strong magnetic field, in the vicinity (ergosphere) of a rapidly rotating blackhole. This topic was created in response to the astrophysical quest to understand the central engines of radio loud extragalactic radio sources. The theory describes a "torsional tug of war" between rotating ergospheric plasma and the distant asymptotic plasma that extracts the rotational inertia of the blackhole. The recoil from the struggle between electromagnetic and gravitational forces near the event horizon is manifested as a powerful pair of magnetized particle beams (jets) that are ejected at nearly the speed of light. These bipolar jets feed large-scale magnetized plasmoids on scales as large as millions of light years (the radio lobes of extragalactic radio sources). This interaction can initiate jets that transport energy fluxes exc...

Modifying the Kerr-Schild transformation used to generate black and white hole spacetimes, new dynamic black and white holes are obtained using a time-dependent Kerr-Schild scalar field. Physical solutions are found for blackholes that shrink with time and for white holes that expand with time. The blackhole spacetimes are physical only in the vicinity of the blackhole, with the physical region increasing in radius with time. The white hole spacetimes are physical throughout. Unlike the standard Schwarzschild solution the singularities are nonisolated, since the time dependence introduces a mass-energy distribution. The surfaces in the metrics where g tt =g rr =0 are dynamic, moving inward with time for the blackholes and outward for the white holes, which leads to a question of whether these spacetimes truly have event horizons--a problem shared with Vaidya's cosmological blackhole spacetimes. By finding a surface that shrinks or expands at the same rate as the null geodesics move, and within which null geodesics move inward or outward faster than the surfaces shrink or expand, respectively, it is verified that these do in fact behave like black and white holes

The 'no-hair' theorem, a key result in general relativity, states that an isolated blackhole is defined by only three parameters: mass, angular momentum, and electric charge; this asymptotic state is reached on a light-crossing time scale. We find that the no-hair theorem is not formally applicable for blackholes formed from the collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively ''frozen in'' the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a blackhole, the latter conserves the number of magnetic flux tubes N B =eΦ ∞ /(πc(ℎ/2π)), where Φ ∞ ≅2π 2 B NS R NS 3 /(P NS c) is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. We test this theoretical result via 3-dimensional general relativistic plasma simulations of rotating blackholes that start with a neutron star dipole magnetic field with no currents initially present outside the event horizon. The blackhole's magnetosphere subsequently relaxes to the split-monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that balds the blackhole on long resistive time scales rather than the short light-crossing time scales expected from the vacuum no-hair theorem.

Binary blackhole mergers are a promising source of gravitational waves for interferometric gravitational wave detectors. Recent advances in numerical relativity have revealed the predictions of General Relativity for the strong burst of radiation generated in the final moments of binary coalescence. We explore features in the merger radiation which characterize the final moments of merger and ringdown. Interpreting the waveforms in terms of an rotating implicit radiation source allows a unified phenomenological description of the system from inspiral through ringdown. Common features in the waveforms allow quantitative description of the merger signal which may provide insights for observations large-mass blackhole binaries.

We present what we believe is the first example of a "λ-line" phase transition in blackhole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid ^{4}He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically anti-de Sitter hairy blackholes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.

A (3 +1 )-dimensional asymptotically flat Kerr blackhole angular speed Ω+ can be used to define an effective spring constant, k =m Ω+2. Its maximum value is the Schwarzschild surface gravity, k =κ , which rapidly weakens as the blackhole spins down and the temperature increases. The Hawking temperature is expressed in terms of the spring constant: 2 π T =κ -k . Hooke's law, in the extremal limit, provides the force F =1 /4 , which is consistent with the conjecture of maximum force in general relativity.

One would expect spacetime to have a foam-like structure on the Planck scale with a very high topology. If spacetime is simply connected (which is assumed in this paper), the non-trivial homology occurs in dimension two, and spacetime can be regarded as being essentially the topological sum of $S^2\\times S^2$ and $K3$ bubbles. Comparison with the instantons for pair creation of blackholes shows that the $S^2\\times S^2$ bubbles can be interpreted as closed loops of virtual blackholes. It is ...

A light-front renormalization group analysis is applied to study matter which falls into massive blackholes, and the related problem of matter with transplankian energies. One finds that the rate of matter spreading over the blackhole's horizon unexpectedly saturates the causality bound. This is related to the transverse growth behavior of transplankian particles as their longitudinal momentum increases. This growth behavior suggests a natural mechanism to implement 't Hooft's scenario that the universe is an image of data stored on a 2 + 1 dimensional hologram-like projection

Beginning with an overview of the theory of blackholes by the editor, this book presents a collection of ten chapters by leading physicists dealing with the variety of quantum mechanical and quantum gravitational effects pertinent to blackholes. The contributions address topics such as Hawking radiation, the thermodynamics of blackholes, the information paradox and firewalls, Monsters, primordial blackholes, self-gravitating Bose-Einstein condensates, the formation of small blackholes in high energetic collisions of particles, minimal length effects in blackholes and small blackholes at the Large Hadron Collider. Viewed as a whole the collection provides stimulating reading for researchers and graduate students seeking a summary of the quantum features of blackholes.

We review the existence of exact hairy blackholes in asymptotically flat, anti-de Sitter and de Sitter space-times. We briefly discuss the issue of stability and the charging of the blackholes with a Maxwell field.

A possible process to destroy a blackhole consists on throwing point particles with sufficiently large angular momentum into the blackhole. In the case of Kerr blackholes, it was shown by Wald that particles with dangerously large angular momentum are simply not captured by the hole, and thus the event horizon is not destroyed. Here we reconsider this gedanken experiment for blackholes in higher dimensions. We show that this particular way of destroying a blackhole does not succeed and that Cosmic Censorship is preserved.

Primordial blackholes have important observational implications through Hawking evaporation and gravitational radiation as well as being a candidate for cold dark matter. Those blackholes are assumed to have formed in the early universe typically with the mass scale contained within the Hubble horizon at the formation epoch and subsequently accreted mass surrounding them. Numerical relativity simulation shows that primordial blackholes of different masses do not accrete much, which contrasts with a simplistic Newtonian argument. We see that primordial blackholes larger than the 'super-horizon' primordial blackholes have decreasing energy and worm-hole like struture, suggesting the formation through quamtum processes.

Among the fascinating phenomena predicted by General Relativity, Einstein's theory of gravity, blackholes and gravitational waves, are particularly important in astronomy. Though once viewed as a mathematical oddity, blackholes are now recognized as the central engines of many of astronomy's most energetic cataclysms. Gravitational waves, though weakly interacting with ordinary matter, may be observed with new gravitational wave telescopes, opening a new window to the universe. These observations promise a direct view of the strong gravitational dynamics involving dense, often dark objects, such as blackholes. The most powerful of these events may be merger of two colliding blackholes. Though dark, these mergers may briefly release more energy that all the stars in the visible universe, in gravitational waves. General relativity makes precise predictions for the gravitational-wave signatures of these events, predictions which we can now calculate with the aid of supercomputer simulations. These results provide a foundation for interpreting expect observations in the emerging field of gravitational wave astronomy.

Motivated by blackhole physics in N = 2,D = 4 supergravity, we study the geometry of quaternionic-K¨ahler manifolds Mobtained by the c-map construction from projective special Kähler manifolds Ms. Improving on earlier treatments, we compute the Käahler potentials on the twistor space Z and Swann

An unexpected interplay between the seemingly disparate fields of M-theory and Quantum Information has recently come to light. We summarise these developments, culminating in a classification of 4-qubit entanglement from the physics of STU blackholes. Based on work done in collaboration with D. Dahanayake, M. J. Duff, H. Ebrahim, A. Marrani and W. Rubens.

An unexpected interplay between the seemingly disparate fields of M-theory and Quantum Information has recently come to light. We summarise these developments, culminating in a classification of 4-qubit entanglement from the physics of STU blackholes. Based on work done in collaboration with D. Dahanayake, M. J. Duff, H. Ebrahim, A. Marrani and W. Rubens.

We apply the warped product space-time scheme to the Banados-Teitelboim-Zanelli blackholes and the Reissner-Nordstroem-anti-de Sitter blackhole to investigate their interior solutions in terms of warped products. It is shown that there exist no discontinuities of the Ricci and Einstein curvatures across event horizons of these blackholes

We show that the interaction between the spin-polarized current and the magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons-the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the implications of magnonic horizons for spin-wave scattering and transport experiments, and for magnon entanglement.

We analyze the statistical mechanics of a gas of neutral and charged blackholes. The microcanonical ensemble is the only possible approach to this system, and the equilibrium configuration is the one for which most of the energy is carried by a single blackhole. Schwarzschild blackholes are found to obey the statistical bootstrap condition. In all cases, the microcanonical temperature is identical to the Hawking temperature of the most massive blackhole in the gas. U(1) charges in general break the bootstrap property. The problems of black-hole decay and of quantum coherence are also addressed

We study the $f(R)$-Maxwell blackhole imposed by constant curvature and its all thermodynamic quantities, which may lead to the Reissner-Nordstr\\"om-AdS blackhole by redefining Newtonian constant and charge. Further, we obtain the $f(R)$-Yang-Mills blackhole imposed by constant curvature, which is related to the Einstein-Yang-Mills blackhole in AdS space. Since there is no analytic blackhole solution in the presence of Yang-Mills field, we obtain asymptotic solutions. Then, we confirm th...

We discuss spherically symmetric exact solutions of the Einstein equations for quintessential matter surrounding a blackhole, which has an additional parameter (ω) due to the quintessential matter, apart from the mass (M). In turn, we employ the Newman-Janis complex transformation to this spherical quintessence blackhole solution and present a rotating counterpart that is identified, for α = -e 2 ≠ 0 and ω = 1/3, exactly as the Kerr-Newman blackhole, and as the Kerr blackhole when α = 0. Interestingly, for a given value of parameter ω, there exists a critical rotation parameter (a = a E ), which corresponds to an extremal blackhole with degenerate horizons, while for a < a E , it describes a nonextremal blackhole with Cauchy and event horizons, and no blackhole for a > a E . We find that the extremal value a E is also influenced by the parameter ω and so is the ergoregion. (orig.)

Full text: We review recent progress that sheds light on the internal structure of general blackholes. We first summarize properties of general multi-charged rotating blackholes both in four and five dimensions. We show that the asymptotic boundary conditions of these general asymptotically flat blackholes can be modified such that a conformal symmetry emerges. These subtracted geometries preserve the thermodynamic properties of the original blackholes and are of the Lifshitz type, thus describing 'a blackhole in the asymptotically conical box'. Recent efforts employ solution generating techniques to construct interpolating geometries between the original blackhole and their subtracted geometries. Upon lift to one dimension higher, these geometries lift to AdS 3 times a sphere, and thus provide a microscopic interpretation of the blackhole entropy in terms of dual two-dimensional conformal field theory. (author)

Our modern understanding of space, time, matter, and even reality itself arose from the three great revolutions of the early twentieth century: special relativity, general relativity, and quantum mechanics. But a century later, this work is unfinished. Many deep connections have been discovered, but the full form of a unified theory incorporating all three principles is not known. Thought experiments and paradoxes have often played a key role in figuring out how to fit theories together. For the unification of general relativity and quantum mechanics, blackholes have been an important arena. I will talk about the quantum mechanics of blackholes, the information paradox, and the latest version of this paradox, the firewall. The firewall points to a conflict between our current theories of spacetime and of quantum mechanics. It may lead to a new understanding of how these are connected, perhaps based on quantum entanglement.

This book is about the life and work of Stephen Hawking. It traces the development of his theories about the universe and particularly blackholes, in a biographical context. Hawking's lecture 'Is the end in sight for theoretical physics' is presented as an appendix. In this, he discusses the possibility of achieving a complete, consistent and unified theory of the physical interactions which would describe all possible observations. (U.K.)

Full Text Available We review black-hole solutions of higher-dimensional vacuum gravity and higher-dimensional supergravity theories. The discussion of vacuum gravity is pedagogical, with detailed reviews of Myers–Perry solutions, black rings, and solution-generating techniques. We discuss black-hole solutions of maximal supergravity theories, including blackholes in anti-de Sitter space. General results and open problems are discussed throughout.

most sensitive scientific instrument ever ... sion, expelling a lot of the mass, but leaving behind a blackhole that is at least ... hole, and indeed such a phenomenon may explain the disappear- ance of a star in the galaxy N6946 [21]. The collapse of stars into blackholes might account for some of the extraordinarily powerful ...

The idea of holography in gravity arose from the fact that the entropy of blackholes is given by their surface area. The holography encountered in gauge/gravity duality has no such relation however; the boundary surface can be placed at an arbitrary location in AdS space and its area does not give the entropy of the bulk. The essential issues are also different between the two cases: in blackholes we get Hawking radiation from the 'holographic surface' which leads to the information issue, while in gauge/gravity duality there is no such radiation. To resolve the information paradox we need to show that there are real degrees of freedom at the horizon of the hole; this is achieved by the fuzzball construction. In gauge/gravity duality we have instead a field theory defined on an abstract dual space; there are no gravitational degrees of freedom at the holographic boundary. It is important to understand the relations and differences between these two notions of holography to get a full understanding of the lessons from the information paradox.

According to the standard view classically blackholes carry no hair, whereas quantum hair is at best exponentially weak. We show that suppression of hair is an artifact of the semi-classical treatment and that in the quantum picture hair appears as an inverse mass-square effect. Such hair is predicted in the microscopic quantum description in which a blackhole represents a self-sustained leaky Bose-condensate of N soft gravitons. In this picture the Hawking radiation is the quantum depletion of the condensate. Within this picture we show that quantum blackhole physics is fully compatible with continuous global symmetries and that global hair appears with the strength B/N, where B is the global charge swallowed by the blackhole. For large charge this hair has dramatic effect on blackhole dynamics. Our findings can have interesting astrophysical consequences, such as existence of blackholes with large detectable baryonic and leptonic numbers.

A strict definition of blackholes is presented and some properties with regard to their mass are enumerated. The Hawking quantum effect - the effect of vacuum instability in the blackhole gravitational field, as a result of shich the blackhole radiates as a heated body is analyzed. It is shown that in order to obtain results on the blackhole radiation it is sufficient to predetermine the in-vacuum state at a time moment in the past, when the collapsing body has a large size, and its gravitational field can be neglected. The causes and the place of particle production by the blackhole, and also the space-time inside the blackhole, are considered

In the classical theory blackholes can only absorb and not emit particles. However it is shown that quantum mechanical effects cause blackholes to create and emit particles. This thermal emission leads to a slow decrease in the mass of the blackhole and to its eventual disappearance: any primordial blackhole of mass less than about 10 15 g would have evaporated by now. Although these quantum effects violate the classical law that the area of the event horizon of a blackhole cannot decrease, there remains a Generalized Second Law: S + 1/4 A never decreases where S is the entropy of matter outside blackholes and A is the sum of the surface areas of the event horizons. This shows that gravitational collapse converts the baryons and leptons in the collapsing body into entropy. It is tempting to speculate that this might be the reason why the Universe contains so much entropy per baryon. (orig.) [de

The origin of supermassive blackholes in the galactic nuclei is quite uncertain in spite of extensive set of observational data. We review the known scenarios of galactic and cosmological formation of supermassive blackholes. The common drawback of galactic scenarios is a lack of time and shortage of matter supply for building the supermassive blackholes in all galaxies by means of accretion and merging. The cosmological scenarios are only fragmentarily developed but propose and pretend to...

The gedanken experiment by Wald to destroy a blackhole using a test particle in the equatorial plane is adapted to the case of extremal magnetized blackholes. We find that the presence of external magnetic fields resulting from the "Ernst magnetization" permits a test particle to have strong enough energy to destroy the blackhole. However, the corresponding effective potentials show that such particles would never reach the horizon.

Physicists are pondering on the possibility of simulating blackholes in the laboratory by means of various "analog models". These analog models, typically based on condensed matter physics, can be used to help us understand general relativity (Einstein's gravity); conversely, abstract techniques developed in general relativity can sometimes be used to help us understand certain aspects of condensed matter physics. This book contains 13 chapters - written by experts in general relativity, particle physics, and condensed matter physics - that explore various aspects of this two-way traffic.

Full Text Available We review some features of Bose–Einstein condensate (BEC models of blackholes obtained by means of the horizon wave function formalism. We consider the Klein–Gordon equation for a toy graviton field coupled to a static matter current in a spherically-symmetric setup. The classical field reproduces the Newtonian potential generated by the matter source, while the corresponding quantum state is given by a coherent superposition of scalar modes with a continuous occupation number. An attractive self-interaction is needed for bound states to form, the case in which one finds that (approximately one mode is allowed, and the system of N bosons can be self-confined in a volume of the size of the Schwarzschild radius. The horizon wave function formalism is then used to show that the radius of such a system corresponds to a proper horizon. The uncertainty in the size of the horizon is related to the typical energy of Hawking modes: it decreases with the increasing of the blackhole mass (larger number of gravitons, resulting in agreement with the semiclassical calculations and which does not hold for a single very massive particle. The spectrum of these systems has two components: a discrete ground state of energy m (the bosons forming the blackhole and a continuous spectrum with energy ω > m (representing the Hawking radiation and modeled with a Planckian distribution at the expected Hawking temperature. Assuming the main effect of the internal scatterings is the Hawking radiation, the N-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy M = Nm and Entropy 2015, 17 6894 a Planckian distribution for E > M at the same Hawking temperature. This can be used to compute the partition function and to find the usual area law for the entropy, with a logarithmic correction related to the Hawking component. The backreaction of modes with ω > m is also shown to reduce

Traditional methods from statistical thermodynamics, with appropriate modifications, are used to study several problems in black-hole thermodynamics. Jaynes's maximum-uncertainty method for computing probabilities is used to show that the earlier-formulated generalized second law is respected in statistically averaged form in the process of spontaneous radiation by a Kerr blackhole discovered by Hawking, and also in the case of a Schwarzschild hole immersed in a bath of black-body radiation, however cold. The generalized second law is used to motivate a maximum-entropy principle for determining the equilibrium probability distribution for a system containing a blackhole. As an application we derive the distribution for the radiation in equilibrium with a Kerr hole (it is found to agree with what would be expected from Hawking's results) and the form of the associated distribution among Kerr black-hole solution states of definite mass. The same results are shown to follow from a statistical interpretation of the concept of black-hole entropy as the natural logarithm of the number of possible interior configurations that are compatible with the given exterior black-hole state. We also formulate a Jaynes-type maximum-uncertainty principle for blackholes, and apply it to obtain the probability distribution among Kerr solution states for an isolated radiating Kerr hole

Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman blackholes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.

The Bekenstein-Hawking entropy for certain BPS-saturated blackholes in string theory has recently been derived by counting internal blackhole microstates at weak coupling. We argue that the blackhole microstate can be measured by interference experiments even in the strong coupling region where there is clearly an event horizon. Extracting information which is naively behind the event horizon is possible due to the existence of statistical quantum hair carried by the blackhole. This quantum hair arises from the arbitrarily large number of discrete gauge symmetries present in string theory. copyright 1996 The American Physical Society

A study of the high angular momentum particles 'atmosphere' near the Schwarzschild blackhole horizon suggested that strong gravitational interactions occur at invariant distance of the order of 3 √M [2]. We present a generalization of this result to the Kerr-Newman blackhole case. It is shown that the larger charge and angular momentum blackhole bears, the larger invariant distance at which strong gravitational interactions occur becomes. This invariant distance is of order 3 √((r + 2 )/((r + - r - ))). This implies that the Planckian structure of the Hawking radiation of extreme blackholes is completely broken

Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form blackholes. The fate of the bubble itself depends on the resulting blackhole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar blackhole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the blackhole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, blackholes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive blackholes. The mechanism of blackhole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical blackholes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a blackhole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse.

We address a long-standing problem of describing the thermodynamics of an accelerating blackhole. We derive a standard first law of blackhole thermodynamics, with the usual identification of entropy proportional to the area of the event horizon-even though the event horizon contains a conical singularity. This result not only extends the applicability of blackhole thermodynamics to realms previously not anticipated, it also opens a possibility for studying novel properties of an important class of exact radiative solutions of Einstein equations describing accelerated objects. We discuss the thermodynamic volume, stability, and phase structure of these blackholes.

A class of braneworld blackholes, which I called as Bronnikov–Melnikov–Dehen (BMD) blackholes, are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate the angular positions and magnifications of relativistic images as well as the time delay between different relativistic images. I also compare the results with those obtained for Schwarzschild and two braneworld blackholes, i.e., the tidal Reissner-Nordström (R-N) and the Casadio–Fabbri–Mazzacurati (CFM) blackholes. (paper)

While there have been many popular-science books on the historical and scientific legacy of Albert Einstein's general theory of relativity, a gap exists in the literature for a definitive, accessible history of the theory's most famous offshoot: blackholes. In BlackHole, the science writer Marcia Bartusiak aims for a discursive middle ground, writing solely about blackholes at a level suitable for both high-school students and more mature readers while also giving some broader scientific context for black-hole research.

In this paper we study the properties of Schwarzschild blackhole surrounded by quintessence matter. The main objective of the paper is to show the existence of Nariai type blackhole for special values of the parameters in the theory. The Nariai blackhole with the quintessence has the topology $dS_2 \\times S_2$ with $dS_2$ with a different scalar curvature than what would be expected for the Schwarzschild-de Sitter degenerate blackhole. Temperature and the entropy for the Schwarzschild-de ...

In backgrounds with compact dimensions there may exist several phases of black objects including a blackhole and a black string. The phase transition between them raises questions and touches on fundamental issues such as topology change, uniqueness, and cosmic censorship. No analytic solution is known for the blackhole, and moreover one can expect approximate solutions only for very small blackholes, while phase transition physics happens when the blackhole is large. Hence we turn to numerical solutions. Here some theoretical background to the numerical analysis is given, while the results will appear in a subsequent paper. The goals for a numerical analysis are set. The scalar charge and tension along the compact dimension are defined and used as improved order parameters which put both the blackhole and the black string at finite values on the phase diagram. The predictions for small blackholes are presented. The differential and the integrated forms of the first law are derived, and the latter (Smarr's formula) can be used to estimate the 'overall numerical error'. Field asymptotics and expressions for physical quantities in terms of the numerical values are supplied. The techniques include the 'method of equivalent charges', free energy, dimensional reduction, and analytic perturbation for small blackholes

was discovered in the constellation Cygnus; a bright X-ray emit- ter associated with a twin-star system, and christened Cygnus X-. 1. It has a massive star and a blackhole orbiting each other. With an optical telescope it is the companion star of the blackhole which is visible, which produces stellar winds blowing away from.

After a brief review of quantum blackhole physics, it is shown how the dynamical properties of a quantum blackhole may be deduced to a large extent from Standard Model Physics, extended to scales near the Planck length, and combined with results from perturbative quantum gravity. Together, these

The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized.......The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized....

The simulated collision event shown is viewed along the beampipe. The event is one in which a microscopic-black-hole was produced in the collision of two protons (not shown). The microscopic-black-hole decayed immediately into many particles. The colors of the tracks show different types of particles emerging from the collision (at the center).

Tipler has claimed that the inward flux of negative energy across the horizon which (according to the semi-classical approximation) accompanies the evaporation of a blackhole would cause a solar mass blackhole to evaporate in less than a second. It is shown that this claim is in error. (orig.)

We review the way the BTZ blackhole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical blackhole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical blackhole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.

We investigate the area spectrum for rotating blackholes which are Kerr and BTZ blackholes. For slowly rotating blackholes, we use the Maggiore's idea combined with Kunstatter's method to derive their area spectra, which are equally spaced.

We investigate the geometry of four dimensional blackhole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge blackholes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge blackhole metric has the same Penrose diagram as the extremal four-charge blackhole. The higher derivative terms lead to another dramatic effect--the gravitational force exerted by a blackhole on an inertial observer is no longer purely attractive. The magnitude of this effect is related to the size of the compactification manifold.

Conceivable experimental investigations to prove the existence of blackholes are discussed. Double system with a blackhole turning around a star-satellite are in the spotlight. X-radiation emmited by such systems and resulting from accretion of the stellar gas by a blackhole, and the gas heating when falling on the blackhole might prove the model suggested. A source of strong X-radiation observed in the Cygnus star cluster and referred to as Cygnus X-1 may be thus identified as a blackhole. Direct registration of short X-ray pulses with msec intervals might prove the suggestion. The lack of appropriate astrophysic facilities is pointed out to be the major difficulty on the way of experimental verifications

Interpreting the cosmological constant as a pressure, whose thermodynamically conjugate variable is a volume, modifies the first law of blackhole thermodynamics. Properties of the resulting thermodynamic volume are investigated: the compressibility and the speed of sound of the blackhole are derived in the case of nonpositive cosmological constant. The adiabatic compressibility vanishes for a nonrotating blackhole and is maximal in the extremal case--comparable with, but still less than, that of a cold neutron star. A speed of sound v s is associated with the adiabatic compressibility, which is equal to c for a nonrotating blackhole and decreases as the angular momentum is increased. An extremal blackhole has v s 2 =0.9 c 2 when the cosmological constant vanishes, and more generally v s is bounded below by c/√(2).

We study self-gravitating, static, spherically symmetric phantom scalar fields with arbitrary potentials (favored by cosmological observations) and single out 16 classes of possible regular configurations with flat, de Sitter, and anti-de Sitter asymptotics. Among them are traversable wormholes, bouncing Kantowski-Sachs (KS) cosmologies, and asymptotically flat blackholes (BHs). A regular BH has a Schwarzschild-like causal structure, but the singularity is replaced by a de Sitter infinity, giving a hypothetic BH explorer a chance to survive. It also looks possible that our Universe has originated in a phantom-dominated collapse in another universe, with KS expansion and isotropization after crossing the horizon. Explicit examples of regular solutions are built and discussed. Possible generalizations include k-essence type scalar fields (with a potential) and scalar-tensor gravity.

We show that a formalism for analyzing the near-horizon conformal symmetry of Schwarzschild blackholes using a scalar field probe is capable of describing blackhole decay. The equation governing blackhole decay can be identified as the geodesic equation in the space of blackhole masses. This provides a novel geometric interpretation for the decay of blackholes. Moreover, this approach predicts a precise correction term to the usual expression for the decay rate of blackholes

The latest achievements in the physics of blackholes are reviewed. The problem of quantum production in a strong gravitational field of blackholes is considered. Another parallel discovered during investigation of interactions between blackholes and between blackholes and surrounding media, is also drawn with thermodynamics. A gravitational field of rotating blackholes is considered. Some cosmological aspects of evaporation of small blackholes are discussed as well as possibilities to observe them

Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive blackholes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of blackholes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating blackholes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the blackhole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the blackhole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the blackhole within the context of the cherished Blandford & Znajek mechanism for blackhole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the blackhole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our

The recent successes of the Laser Interferometer Gravitational-Wave Observatory (LIGO) has raised hopes that several long-standing questions in black-hole physics will soon be answerable. Besides revealing how the black-hole binary pairs are built, could detections with LIGO also reveal how the blackholes themselves form?Isolation or HierarchyThe first detection of gravitational waves, GW150914, was surprising for a number of reasons. One unexpected result was the mass of the two blackholes that LIGO saw merging: they were a whopping 29 and 36 solar masses.On the left of this schematic, two first-generation (direct-collapse) blackholes form a merging binary. The right illustrates a second-generation hierarchical merger: each blackhole in the final merging binary was formed by the merger of two smaller blackholes. [Adapted fromGerosa et al., a simultaneously published paper that also explores the problem of hierarchical mergers and reaches similar conclusions]How do blackholes of this size form? One possibility is that they form in isolation from the collapse of a single massive star. In an alternative model, they are created through the hierarchical merger of smaller blackholes, gradually building up to the size we observed.A team of scientists led by Maya Fishbach (University of Chicago) suggests that we may soon be able to tell whether or not blackholes observed by LIGO formed hierarchically. Fishbach and collaborators argue that hierarchical formation leaves a distinctive signature on the spins of the final blackholes and that as soon as we have enough merger detections from LIGO, we can use spin measurements to statistically determine if LIGO blackholes were formed hierarchically.Spins from Major MergersWhen two blackholes merge, both their original spins and the angular momentum of the pair contribute to the spin of the final blackhole that results. Fishbach and collaborators calculate the expected distribution of these final spins assuming that

The spacetime singularities in classical general relativity are inevitable, as predicated by the celebrated singularity theorems. However, it is a general belief that singularities do not exist in Nature and that they are the limitations of the general relativity. In the absence of a welldefined quantum gravity, models of regular blackholes have been studied. We employ a probability distribution inspired mass function m(r) to replace the Kerr blackhole mass M to represent a nonsingular rotating blackhole that is identified asymptotically (r >> k, k > 0 constant) exactly as the Kerr-Newman blackhole, and as the Kerr blackhole when k = 0. The radiating counterpart renders a nonsingular generalization of Carmeli's spacetime as well as Vaidya's spacetime, in the appropriate limits. The exponential correction factor changing the geometry of the classical blackhole to remove the curvature singularity can also be motivated by quantum arguments. The regular rotating spacetime can also be understood as a blackhole of general relativity coupled to nonlinear electrodynamics. (orig.)

We revisit the study of (A)dS blackholes in Lovelock theories. We present a new tool that allows to attack this problem in full generality. In analyzing maximally symmetric Lovelock blackholes with non-planar horizon topologies, many distinctive and interesting features are observed. Among them, the existence of maximally symmetric vacua does not support blackholes in vast regions of the space of gravitational couplings, multi-horizon blackholes and branches of solutions that suggest the existence of a rich diagram of phase transitions. The appearance of naked singularities seems unavoidable in some cases, raising the question about the fate of the cosmic censorship conjecture in these theories. There is a preferred branch of solutions for planar blackholes, as well as for non-planar blackholes with high enough mass or temperature. Our study clarifies the role of all branches of solutions, including asymptotically dS blackholes, and whether they should be considered when studying these theories in the context of AdS/CFT. (paper)

The popular conception of blackholes reflects the behavior of the massive blackholes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of blackholes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.

We consider the spacetime structure of Kerr-Goedel blackholes, analyzing their parameter space in detail. We apply the tunnelling method to compute their temperature and compare the results to previous calculations obtained via other methods. We claim that it is not possible to have the closed timelike curve (CTC) horizon in between the two blackhole horizons and include a discussion of issues that occur when the radius of the CTC horizon is smaller than the radius of both blackhole horizons

BLACKHOLES A TRAVELER'S GUIDE Clifford Pickover's inventive and entertaining excursion beyond the curves of space and time. "I've enjoyed Clifford Pickover's earlier books . . . now he has ventured into the exploration of blackholes. All would-be tourists are strongly advised to read his traveler's guide." -Arthur C. Clarke. "Many books have been written about blackholes, but none surpass this one in arousing emotions of awe and wonder towards the mysterious structure of the universe." -Martin Gardner. "Bucky Fuller thought big. Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." -Wired. "The book is fun, zany, in-your-face, and refreshingly addictive." -Times Higher Education Supplement.

We compute the length and time scales associated with resonant orbits around Kerr blackholes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the blackhole, or in the frequencies of quasiperiodic oscillations for accreting blackholes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.

The popular conception of blackholes reflects the behavior of the massive blackholes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of blackholes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.

We consider the possibility that small blackholes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible when generic quantum gravity corrections are added to the Higgs potential, we show that primordial blackholes can stimulate vacuum decay. We demonstrate that for suitable parameter ranges, the vacuum decay process dominates over the Hawking evaporation process. Finally, we comment on the application of these results to vacuum decay seeded by blackholes produced in particle collisions.

The gravitational polarizability properties of blackholes are compared and contrasted with their electromagnetic polarizability properties. The 'shape' or 'height' multipolar Love numbers h l of a blackhole are defined and computed. They are then compared to their electromagnetic analogs h l EM . The Love numbers h l give the height of the lth multipolar 'tidal bulge' raised on the horizon of a blackhole by faraway masses. We also discuss the shape of the tidal bulge raised by a test-mass m, in the limit where m gets very close to the horizon.

We study the effect of primordial blackholes on the classical rate of nucleation of AdS regions within the standard electroweak vacuum. We find that the energy barrier for transitions to the new vacuum, which characterizes the exponential suppression of the nucleation rate, can be reduced significantly in the black-hole background. A precise analysis is required in order to determine whether the the existence of primordial blackholes is compatible with the form of the Higgs potential at high temperature or density in the Standard Model or its extensions.

We study phase transitions between blackholes with scalar hair and topological blackholes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ blackhole in three dimensions and topological blackhole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between blackhole with scalar hair (Martinez-Troncoso-Zanelli blackhole) and topological blackhole is second-order by usi...

New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of blackholes may shut off the high-speed jets they produce. These results suggest that these blackholes have a mechanism for regulating the rate at which they grow. Blackholes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass blackholes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass blackholes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a blackhole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the blackhole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the blackhole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this blackhole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don

This paper reviews the current status of blackhole (BH) astrophysics, focusing on topics of interest to a physics audience. Astronomers have discovered dozens of compact objects with masses greater than 3M o-dot , the likely maximum mass of a neutron star. These objects are identified as BH candidates. Some of the candidates have masses ∼5M o-dot -20M o-dot and are found in x-ray binaries, while the rest have masses ∼10 6 M o-dot -10 9.5 M o-dot and are found in galactic nuclei. A variety of methods are being tried to estimate the spin parameters of the candidate BHs. There is strong circumstantial evidence that many of the objects have event horizons, so there is good reason to believe that the candidates are true BHs. Recent MHD simulations of magnetized plasma accreting on rotating BHs seem to hint that relativistic jets may be produced by a magnetic analogue of the Penrose process

After a brief review of quantum blackhole physics, it is shown how the dynamical properties of a quantum blackhole may be deduced to a large extent from Standard Model Physics, extended to scales near the Planck length, and combined with results from perturbative quantum gravity. Together, these interactions generate a Hilbert space of states on the blackhole horizon, which can be investigated, displaying interesting systematics by themselves. To make such approaches more powerful, a study is made of the blackhole complementarity principle, from which one may deduce the existence of a hidden form of local conformal invariance. Finally, the question is raised whether the principles underlying Quantum Mechanics are to be sharpened in this domain of physics as well. There are intriguing possibilities.

A paradigm describing blackhole evaporation in non-perturbative quantum gravity is developed by combining two sets of detailed results: (i) resolution of the Schwarzschild singularity using quantum geometry methods and (ii) time evolution of blackholes in the trapping and dynamical horizon frameworks. Quantum geometry effects introduce a major modification in the traditional spacetime diagram of blackhole evaporation, providing a possible mechanism for recovery of information that is classically lost in the process of blackhole formation. The paradigm is developed directly in the Lorentzian regime and necessary conditions for its viability are discussed. If these conditions are met, much of the tension between expectations based on spacetime geometry and structure of quantum theory would be resolved

In the spirit of blackhole complementary principle, we have found the noncommutative membrane of Scharzchild blackholes. In this paper we extend our results to Kerr blackhole and see the same story. Also we make a conjecture that spacetimes are noncommutative on the stretched membrane of the more general Kerr-Newman blackhole.

Primordial blackholes evaporate due to Hawking radiation. We find that the evaporation times of primordial blackholes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial blackholes are existing today, which strengthens the conjecture that the primordial blackholes ...

It is argued that models of extended inflation, in which modified Einstein gravity allows a graceful exit from the false vacuum, lead to copious production of blackholes. The critical temperature of the inflationary phase transition must be >10 8 GeV in order to avoid severe cosmological problems in a universe dominated by blackholes. We speculate on the possibility that the interiors of false vacuum regions evolve into baby universes. (orig.)

While the energy of the universe has been established to be about 0.04 baryons, 0.24 dark matter and 0.72 dark energy, the cosmological entropy is almost entirely, about $(1 - 10^{-15})$, from blackholes and only $10^{-15}$ from everything else. This identification of all dark matter as blackholes is natural in statistical mechanics. Cosmological history of dark matter is discussed.

We use the AdS/CFT correspondence in a regime where the field theory is well described by fluid mechanics to study large blackholes in asymptotically locally anti de Sitter spaces. In particular, we use the fluid description to study the thermodynamics of the blackholes and the existence of exotic horizon topologies in higher dimensions. First we test this method by comparing large rotating blackholes in global AdSD spaces to stationary solutions of the relativistic Navier-Stokes equations on SD-2. Reading off the equation of state of this fluid from the thermodynamics of non-rotating blackholes, we proceed to construct the nonlinear spinning solutions of fluid mechanics that are dual to rotating blackholes. In all known examples, the thermodynamics and the local stress tensor of our solutions are in precise agreement with the thermodynamics and boundary stress tensor of the spinning blackholes. Our results yield predictions for the thermodynamics of all large blackholes in all theories of gravity on AdS spaces, for example, IIB string theory on AdS5 x S 5 and M theory on AdS4 x S7 and AdS7 x S 4. We then construct solutions to the relativistic Navier-Stokes equations that describe the long wavelength collective dynamics of the deconfined plasma phase of N = 4 Yang Mills theory compactified down to d = 3 on a Scherk-Schwarz circle. Our solutions are stationary, axially symmetric spinning balls and rings of plasma. These solutions, which are dual to (yet to be constructed) rotating blackholes and black rings in Scherk-Schwarz compactified AdS 5, and have properties that are qualitatively similar to those of blackholes and black rings in flat five dimensional gravity. We also study the stability of these solutions to small fluctuations, which provides an indirect method for studying Gregory-Laflamme instabilities. We also extend the construction to higher dimensions, allowing one to study the existence of new blackhole topologies and their phase diagram.

The physics of blackholes is explored in terms of a membrane paradigm which treats the event horizon as a two-dimensional membrane embedded in three-dimensional space. A 3+1 formalism is used to split Schwarzschild space-time and the laws of physics outside a nonrotating hole, which permits treatment of the atmosphere in terms of the physical properties of thin slices. The model is applied to perturbed slowly or rapidly rotating and nonrotating holes, and to quantify the electric and magnetic fields and eddy currents passing through a membrane surface which represents a stretched horizon. Features of tidal gravitational fields in the vicinity of the horizon, quasars and active galalctic nuclei, the alignment of jets perpendicular to accretion disks, and the effects of blackholes at the center of ellipsoidal star clusters are investigated. Attention is also given to a blackhole in a binary system and the interactions of blackholes with matter that is either near or very far from the event horizon. Finally, a statistical mechanics treatment is used to derive a second law of thermodynamics for a perfectly thermal atmosphere of a blackhole

While physicists have been grappling with the theory of blackholes (BH), as shown by the many contributions to the Einstein year, astronomers have been successfully searching for real blackholes in the Universe. Blackhole astrophysics began in the 1960s with the discovery of quasars and other active galactic nuclei (AGN) in distant galaxies. Already in the 1960s it became clear that the most natural explanation for the quasar activity is the release of gravitational energy through accretion of gas onto supermassive blackholes. The remnants of this activity have now been found in the centers of about 50 nearby galaxies. BH astrophysics received a new twist in the 1970s with the discovery of the X-ray binary (XRB) Cygnus X-1. The X-ray emitting compact object was too massive to be explained by a neutron star. Today, about 20 excellent BH candidates are known in XRBs. On the extragalactic scale, more than 100.000 quasars have been found in large galaxy surveys. At the redshift of the most distant ones, the Universe was younger than one billion year. The most enigmatic blackhole candidates identified in the last years are the compact objects behind the Gamma-Ray Bursters. The formation of all these types of blackholes is accompanied by extensive emission of gravitational waves. The detection of these strong gravity events is one of the biggest challenges for physicists in the near future. (author)

Angular momentum, or spin, is one of only two fundamental properties of astrophysical blackholes, and measuring its value has numerous applications. For instance, obtaining reliable spin measurements could constrain the growth history of supermassive blackholes and reveal whether relativistic jets are powered by tapping into the blackhole spin reservoir. The two well-established techniques for measuring blackhole spin can both be applied to X-ray binaries, but are in disagreement for cases of non-maximal spin. This discrepancy must be resolved if either technique is to be deemed robust. We show that the technique based on disc continuum fitting is sensitive to uncertainties regarding the disc atmosphere, which are observationally unconstrained. By incorporating reasonable uncertainties into blackhole spin probability density functions, we demonstrate that the spin measured by disc continuum fitting can become highly uncertain. Future work toward understanding how the observed disc continuum is altered by atmospheric physics, particularly magnetic fields, will further strengthen blackhole spin measurement techniques.

We propose that any blackhole has atomic structure in its inside and has no horizon as a model of blackholes. Our proposal is founded on a mean field approximation of gravity. The structure of our model consists of a (charged) singularity at the center and quantum fluctuations of fields around the singularity, namely, it is quite similar to that of atoms. Any properties of blackholes, e.g. entropy, can be explained by the model. The model naturally quantizes blackholes. In particular, we find the minimum blackhole, whose structure is similar to that of the hydrogen atom and whose Schwarzschild radius is approximately 1.1287 times the Planck length. Our approach is conceptually similar to Bohr's model of the atomic structure, and the concept of the minimum Schwarzschild radius is similar to that of the Bohr radius. The model predicts that blackholes carry baryon number, and the baryon number is rapidly violated. This baryon number violation can be used as verification of the model. (author)

Introducing a blackhole (BH) effective temperature, which takes into account both the non-strictly thermal character of Hawking radiation and the countable behavior of emissions of subsequent Hawking quanta, we recently re-analysed BH quasi-normal modes (QNMs) and interpreted them naturally in terms of quantum levels. In this work we improve such an analysis removing some approximations that have been implicitly used in our previous works and obtaining the corrected expressions for the formulas of the horizon's area quantization and the number of quanta of area and hence also for Bekenstein-Hawking entropy, its subleading corrections and the number of micro-states, i.e. quantities which are fundamental to realize the underlying quantum gravity theory, like functions of the QNMs quantum "overtone" number n and, in turn, of the BH quantum excited level. An approximation concerning the maximum value of n is also corrected. On the other hand, our previous results were strictly corrected only for scalar and gravitational perturbations. Here we show that the discussion holds also for vector perturbations. The analysis is totally consistent with the general conviction that BHs result in highly excited states representing both the "hydrogen atom" and the "quasi-thermal emission" in quantum gravity. Our BH model is somewhat similar to the semi-classical Bohr's model of the structure of a hydrogen atom. The thermal approximation of previous results in the literature is consistent with the results in this paper. In principle, such results could also have important implications for the BH information paradox.

We find a new blackhole in three dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative blackhole. This is a regular blackhole with two horizons. We compare thermodynamics of this blackhole with that of non-rotating BTZ blackhole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy.

We study blackholes in the Horava-Lifshitz gravity with a parameter λ. For 1/3≤λ 3, the blackholes behave the Reissner-Nordstroem type blackhole in asymptotically flat spacetimes. Hence, these all are quite different from the Schwarzschild-AdS blackhole of Einstein gravity. The temperature, mass, entropy, and heat capacity are derived for investigating thermodynamic properties of these blackholes. (orig.)

We study the prospect of the Gaia satellite to identify blackhole binary systems by detecting the orbital motion of the companion stars. Taking into account the initial mass function, mass transfer, common envelope phase, interstellar absorption and identifiability of blackholes, we estimate the number of blackhole binaries detected by Gaia and their distributions with respect to the blackhole mass for several models with different parameters. We find that $\\sim 300-6000$ blackhole binar...

We review the recently established relationships between blackhole entropy in string theory and the quantum entanglement of qubits and qutrits in quantum information theory. The first example is provided by the measure of the tripartite entanglement of three qubits (Alice, Bob and Charlie), known as the 3-tangle, and the entropy of the 8-charge STU blackhole of N=2 supergravity, both of which are given by the [SL(2)] 3 invariant hyperdeterminant, a quantity first introduced by Cayley in 1845. Moreover the classification of three-qubit entanglements is related to the classification of N=2 supersymmetric STU blackholes. There are further relationships between the attractor mechanism and local distillation protocols and between supersymmetry and the suppression of bit flip errors. At the microscopic level, the blackholes are described by intersecting D3-branes whose wrapping around the six compact dimensions T 6 provides the string-theoretic interpretation of the charges and we associate the three-qubit basis vectors, |ABC>(A,B,C=0 or 1), with the corresponding 8 wrapping cycles. The blackhole/qubit correspondence extends to the 56 charge N=8 blackholes and the tripartite entanglement of seven qubits where the measure is provided by Cartan's E 7 contains [SL(2)] 7 invariant. The qubits are naturally described by the seven vertices ABCDEFG of the Fano plane, which provides the multiplication table of the seven imaginary octonions, reflecting the fact that E 7 has a natural structure of an O-graded algebra. This in turn provides a novel imaginary octonionic interpretation of the 56=7x8 charges of N=8: the 24=3x8 NS-NS charges correspond to the three imaginary quaternions and the 32=4x8 R-R to the four complementary imaginary octonions. We contrast this approach with that based on Jordan algebras and the Freudenthal triple system. N=8 blackholes (or black strings) in five dimensions are also related to the bipartite entanglement of three qutrits (3-state systems

Unique observations of the flickering light from the surroundings of two blackholes provide new insights into the colossal energy that flows at their hearts. By mapping out how well the variations in visible light match those in X-rays on very short timescales, astronomers have shown that magnetic fields must play a crucial role in the way blackholes swallow matter. Flickering blackhole ESO PR Photo 36/08 Flickering blackhole Like the flame from a candle, light coming from the surroundings of a blackhole is not constant -- it flares, sputters and sparkles. "The rapid flickering of light from a blackhole is most commonly observed at X-ray wavelengths," says Poshak Gandhi, who led the international team that reports these results. "This new study is one of only a handful to date that also explore the fast variations in visible light, and, most importantly how these fluctuations relate to those in X-rays." The observations tracked the shimmering of the blackholes simultaneously using two different instruments, one on the ground and one in space. The X-ray data were taken using NASA's Rossi X-ray Timing Explorer satellite. The visible light was collected with the high speed camera ULTRACAM, a visiting instrument at ESO's Very Large Telescope (VLT), recording up to 20 images a second. ULTRACAM was developed by team members Vik Dhillon and Tom Marsh. "These are among the fastest observations of a blackhole ever obtained with a large optical telescope," says Dhillon. To their surprise, astronomers discovered that the brightness fluctuations in the visible light were even more rapid than those seen in X-rays. In addition, the visible-light and X-ray variations were found not to be simultaneous, but to follow a repeated and remarkable pattern: just before an X-ray flare the visible light dims, and then surges to a bright flash for a tiny fraction of a second before rapidly decreasing again. None of this radiation emerges directly from the blackhole, but from the

The blackhole saga spanning some seventy years may be broadly divided into four phases, namely, (a) the dark ages when little was known about blackholes even though they had come into existence quite early through the Schwarzschild solution, (b) the age of enlightenment bringing in deep and prolific discoveries, (c) the age of fantasy that cast blackholes in all sorts of extraordinary roles, and (d) the golden age of relativistic astrophysics - to some extent similar to Dirac's characterisation of the development of quantum theory - in which blackholes have been extensively used to elucidate a number of astrophysical phenomena. It is impossible to give here even the briefest outline of the major developments in this vast area. We shall only attempt to present a few aspects of blackhole physics which have been actively pursued in the recent past. Some details are given in the case of those topics that have not found their way into text books or review articles. (author)

Cosmologies containing a substantial amount of matter in the form of evaporating primordial blackholes are investigated. A review of constraints on the numbers of such blackholes, including an analysis of a new limit found by looking at the destruction of deuterium by high energy photons, shows that there must be a negligible population of small blackholes from the era of cosmological nucleosynthesis onwards, but that there are no strong constraints before this time. The major part of the work is based on the construction of detailed, self-consistent cosmological models in which blackholes are continually forming and evaporating The interest in these models centres on the question of baryon generation, which occurs via the asymmetric decay of a new type of particle which appears as a consequence of the recently developed Grand Unified Theories of elementary particles. Unfortunately, there is so much uncertainty in the models that firm conclusions are difficult to reach; however, it seems feasible in principle that primordial blackholes could be responsible for a significant part of the present matter density of the Universe. (author)

Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar blackhole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the blackhole," says lead author Manfred Pakull. "This blackhole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain blackholes with masses of a few million times that of the Sun." Blackholes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some blackholes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the blackhole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the blackhole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the blackhole from which they are launched," says co-author Robert Soria [1]. "If the blackhole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

Galaxies are the basic unit of cosmology. The study of galaxy formation is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning. The physics of galaxy formation is complicated because it deals with the dynamics of stars, thermodynamics of gas and energy production of stars. A blackhole is a massive object whose gravitational field is so intense that it prevents any form of matter or radiation to escape. It is hypothesized that the most massive galaxies in the universe- "elliptical galaxies"- grow simultaneously with the supermassive blackholes at their centers, giving us much stronger evidence that blackholes control galaxy formation. This book reviews new evidence in the field.

Evidence has been accumulating for several decades that many galaxies harbor central mass concentrations that may be in the form of blackholes with masses between a few million to a few billion time the mass of the Sun. I will discuss measurements over the last two decades, employing adaptive optics imaging and spectroscopy on large ground-based telescopes that prove the existence of such a massive blackhole in the Center of our Milky Way, beyond any reasonable doubt. These data also provide key insights into its properties and environment. Most recently, a tidally disrupting cloud of gas has been discovered on an almost radial orbit that reached its peri-distance of ~2000 Schwarzschild radii in 2014, promising to be a valuable tool for exploring the innermost accretion zone. Future interferometric studies of the Galactic Center Blackhole promise to be able to test gravity in its strong field limit.

Ever since the discovery of blackhole evaporation, the region of origin of the radiated quanta has been a topic of debate. Recently it was argued by Giddings that the Hawking quanta originate from a region well outside the blackhole horizon by calculating the effective radius of a radiating body via the Stefan-Boltzmann law. In this paper we try to further explore this issue and end up corroborating this claim, using both a heuristic argument and a detailed study of the stress energy tensor. We show that the Hawking quanta originate from what might be called a quantum atmosphere around the blackhole with energy density and fluxes of particles peaked at about 4 MG, running contrary to the popular belief that these originate from the ultra high energy excitations very close to the horizon. This long distance origin of Hawking radiation could have a profound impact on our understanding of the information and transplanckian problems.

Full Text Available Ever since the discovery of blackhole evaporation, the region of origin of the radiated quanta has been a topic of debate. Recently it was argued by Giddings that the Hawking quanta originate from a region well outside the blackhole horizon by calculating the effective radius of a radiating body via the Stefan–Boltzmann law. In this paper we try to further explore this issue and end up corroborating this claim, using both a heuristic argument and a detailed study of the stress energy tensor. We show that the Hawking quanta originate from what might be called a quantum atmosphere around the blackhole with energy density and fluxes of particles peaked at about 4MG, running contrary to the popular belief that these originate from the ultra high energy excitations very close to the horizon. This long distance origin of Hawking radiation could have a profound impact on our understanding of the information and transplanckian problems.

Blackholes are a constant source of fascination to many due to their mysterious nature. BlackHoles: A Very Short Introduction addresses a variety of questions, including what a blackhole actually is, how they are characterized and discovered, and what would happen if you came too close to one. It explains how blackholes form and grow—by stealing material that belongs to stars—as well as how many there may be in the Universe. It also explores the large blackholes found in the centres of galaxies, and how blackholes power quasars and lie behind other spectacular phenomena in the cosmos.

Full text: A geometric inequality in General Relativity relates quantities that have both a physical interpretation and a geometrical definition. It is well known that the parameters that characterize the Kerr-Newman blackhole satisfy several important geometric inequalities. Remarkably enough, some of these inequalities also hold for dynamical blackholes. This kind of inequalities, which are valid in the dynamical and strong field regime, play an important role in the characterization of the gravitational collapse. They are closed related with the cosmic censorship conjecture. In this talk I will review recent results in this subject. (author)

Full text: A geometric inequality in General Relativity relates quantities that have both a physical interpretation and a geometrical definition. It is well known that the parameters that characterize the Kerr-Newman blackhole satisfy several important geometric inequalities. Remarkably enough, some of these inequalities also hold for dynamical blackholes. This kind of inequalities, which are valid in the dynamical and strong field regime, play an important role in the characterization of the gravitational collapse. They are closed related with the cosmic censorship conjecture. In this talk I will review recent results in this subject. (author)

This paper extends to the case of charged rotating blackholes the conformally stationary, axisymmetric, conformally separable solutions presented for uncharged rotating blackholes in a companion paper. In the present paper, the collisionless fluid accreted by the blackhole may be charged. The charge of the blackhole is determined self-consistently by the charge accretion rate. As in the uncharged case, hyper-relativistic counterstreaming between ingoing and outgoing streams drives inflation at (just above) the inner horizon, followed by collapse. If both ingoing and outgoing streams are charged, then conformal separability holds during early inflation, but fails as inflation develops. If conformal separability is imposed throughout inflation and collapse, then only one of the ingoing and outgoing streams can be charged: the other must be neutral. Conformal separability prescribes a hierarchy of boundary conditions on the ingoing and outgoing streams incident on the inner horizon. The dominant radial boundary conditions require that the incident ingoing and outgoing number densities be uniform with latitude, but the charge per particle must vary with latitude such that the incident charge densities vary in proportion to the radial electric field. The subdominant angular boundary conditions require specific forms of the incident number- and charge-weighted angular motions. If the streams fall freely from outside the horizon, then the prescribed angular conditions can be achieved by the charged stream, but not by the neutral stream. Thus, as in the case of an uncharged blackhole, the neutral stream must be considered to be delivered ad hoc to just above the inner horizon.

We investigate the microscopic origin of blackhole entropy, in particular the gap between the maximum entropy of ordinary matter and that of blackholes. Using curved space, we construct configurations with entropy greater than the area A of a blackhole of equal mass. These configurations have pathological properties and we refer to them as monsters. When monsters are excluded we recover the entropy bound on ordinary matter S 3/4 . This bound implies that essentially all of the microstates of a semiclassical blackhole are associated with the growth of a slightly smaller blackhole which absorbs some additional energy. Our results suggest that the area entropy of blackholes is the logarithm of the number of distinct ways in which one can form the blackhole from ordinary matter and smaller blackholes, but only after the exclusion of monster states

We examine the entropy of blackholes in de Sitter space and blackholes surrounded by quintessence. These blackholes have multiple horizons, including at least the blackhole event horizon and a horizon outside it (cosmological horizon for de Sitter blackholes and "quintessence horizon" for the blackholes surrounded by quintessence). Based on the consideration that the two horizons are not independent each other, we conjecture that the total entropy of these blackholes should not be simply the sum of entropies of the two horizons, but should have an extra term coming from the correlations between the two horizons. Different from our previous works, in this paper we consider the cosmological constant as the variable and employ an effective method to derive the explicit form of the entropy. We also try to discuss the thermodynamic stabilities of these blackholes according to the entropy and the effective temperature.

The membrane formalism is applied to various types of gravitational perturbations of a blackhole. Attention is given to the disturbance of the horizon of a blackhole by compact masses lowered toward a nonrotating hole and the deformations experienced by a rotating hole. Nonaxisymmetric gravitational tidal fields in rigid motion about a rotating hole are considered, along with the behavior of massive particle moving along the equator of a rotating hole, and the spindown of a rotating hole in an external tidal field. The extraction of rotational energy from a blackhole by orbiting bodies is examined, as are superradiant scattering of gravitational waves and the quasi-normal modes of a blackhole. The perturbations imparted to a blackhole by a compact body plunging into the membrane (a stretched horizon) at a velocity close to the local light speed and by a radially accelerated particle above the horizon of a nonrotating hole are also explored

Current technologies have enabled glimpses at the many facetsof blackholes, which we know to be plentiful in our cosmos.A panoramic view of the evidence for them is presented hereacross the large range of masses that they span. Author Affiliations. Prajval Shastri. Resonance – Journal of Science Education.

Pinhole photography has made major contributions to astrophysics through the use of “coded apertures”. Coded apertures were instrumental in locating gamma-ray bursts and proving that they originate in faraway galaxies, some from the birth of blackholes from the first stars that formed just after the big bang.

Full Text Available Exotic spin structures are non-trivial liftings, of the orthogonal bundle to the spin bundle, on orientable manifolds that admit spin structures according to the celebrated Geroch theorem. Exotic spin structures play a role of paramount importance in different areas of physics, from quantum field theory, in particular at Planck length scales, to gravity, and in cosmological scales. Here, we introduce an in-depth panorama in this field, providing blackhole physics as the fount of spacetime exoticness. Blackholes are then studied as the generators of a non-trivial topology that also can correspond to some inequivalent spin structure. Moreover, we investigate exotic spinor fields in this context and the way exotic spinor fields branch new physics. We also calculate the tunneling probability of exotic fermions across a Kerr-Sen blackhole, showing that the exotic term does affect the tunneling probability, altering the blackhole evaporation rate. Finally we show that it complies with the Hawking temperature universal law.

It is a common wisdom that properties of macroscopic bodies are well described by (semi)classical physics. As we have suggested this wisdom is not applicable to blackholes. Despite being macroscopic, blackholes are quantum objects. They represent Bose-Einstein condensates of N-soft gravitons at the quantum critical point, where N Bogoliubov modes become gapless. As a result, physics governing arbitrarily-large blackholes (e.g., of galactic size) is a quantum physics of the collective Bogoiliubov modes. This fact introduces a new intrinsically-quantum corrections in form of 1/N, as opposed to exp(-N). These corrections are unaccounted by the usual semiclassical expansion in h and cannot be recast in form of a quantum back-reaction to classical metric. Instead the metric itself becomes an approximate entity. These 1/N corrections abolish the presumed properties of blackholes, such as non existence of hair, and are the key to nullifying the so-called information paradox.

Offers a selected bibliography pertaining to blackholes with the following categories: introductory books; introductory articles; somewhat more advanced articles; readings about Einstein's general theory of relativity; books on the death of stars; articles on the death of stars; specific articles about Supernova 1987A; relevant science fiction…

An accreting blackhole is, by definition, characterized by the drain. Namely, the matter falls into a blackhole much the same way as water disappears down a drain matter goes in and nothing comes out. As this can only happen in a blackhole, it provides a way to see ``a blackhole'', an unique observational signature. The accretion proceeds almost in a free-fall manner close to the blackhole horizon, where the strong gravitational field dominates the pressure forces. In this paper we present analytical calculations and Monte-Carlo simulations of the specific features of X-ray spectra formed as a result of upscattering of the soft (disk) photons in the converging inflow (CI) into the blackhole. The full relativistic treatment has been implemented to reproduce these spectra. We show that spectra in the soft state of blackhole systems (BHS) can be described as the sum of a thermal (disk) component and the convolution of some fraction of this component with the CI upscattering spread (Greens) function. The latter boosted photon component is seen as an extended power-law at energies much higher than the characteristic energy of the soft photons. We demonstrate the stability of the power spectral index over a wide range of the plasma temperature 0 - 10 keV and mass accretion rates (higher than 2 in Eddington units). We also demonstrate that the sharp high energy cutoff occurs at energies of 200-400 keV which are related to the average energy of electrons mec2 impinging upon the event horizon. The spectrum is practically identical to the standard thermal Comptonization spectrum when the CI plasma temperature is getting of order of 50 keV (the typical ones for the hard state of BHS). In this case one can see the effect of the bulk motion only at high energies where there is an excess in the CI spectrum with respect to the pure thermal one. Furthermore we demonstrate that the change of spectral shapes from the soft X-ray state to the hard X-ray state is clearly to be

The processes of spontaneous and induced production and accumulation of charged bosons on quasibound superradiant levels in the field of Kerr-Newman blackhole is analysed. It is shown that bosonic instability may be caused exclusively by the rotation of the blackhole. Particulary, the Reissner-Nordstrom configuration is stable. In the case of rotating and charged blackhole the bosonic instability may cause an increase of charge of the blackhole

Holographic theories representing blackholes are expected to exhibit quantum chaos. We argue if the laws of quantum mechanics are expected to hold for observers inside such blackholes, then such holographic theories must have a mean field approximation valid for typical blackhole states, and for timescales approaching the scrambling time. Using simple spin models as examples, we examine the predictions of such an approach for observers inside blackholes, and more speculatively inside cosmological horizons.

A unified framework for blackholes and traversible wormholes is described, where both are locally defined by outer trapping horizons, two-way traversible for wormholes and one-way traversible for black or white holes. In a two-dimensional dilaton gravity model, examples are given of: construction of wormholes from blackholes; operation of wormholes for transport, including back-reaction; maintenance of an operating wormhole; and collapse of wormholes to blackholes. In spherically symmetric...

The Babichev-Dokuchaev-Eroshenko model for the accretion of dark energy onto blackholes has been extended to deal with blackholes with non-static metrics. The possibility that for an asymptotic observer a blackhole with large mass will rapidly increase and eventually engulf the Universe at a finite time in the future has been studied by using reasonable values for astronomical parameters. It is concluded that such a phenomenon is forbidden for all blackholes in quintessential cosmological models

What is the nature of the energy spectrum of a blackhole ? The algebraic approach to blackhole quantization requires the horizon area eigenvalues to be equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be exponentially degenerate with respect to the area quantum number if one is to understand blackhole entropy as reflecting degeneracy of the observable states. Here we construct the blackhole states by means of a pair of "creation operators" subject to a particular...

Does a dynamical blackhole embedded in a cosmological FRW background emit Hawking radiation where a globally defined event horizon does not exist? What are the differences to the Schwarzschild blackhole? What about the first law of blackhole mechanics? We face these questions using the LTB cosmological blackhole model recently published. Using the Hamilton-Jacobi and radial null geodesic-methods suitable for dynamical cases, we show that it is the apparent horizon which contributes to the...

A possible link between EPR-type quantum phenomena and astrophysical objects like blackholes, under a new general definition of entanglement, is established. A new approach, involving backward time evolution and topology changes, is presented bringing to a definition of the system blackhole-worm hole-white hole as an entangled system.

Blackholes and gravitational waves are theoretical entities of today astrophysics. Various observed phenomena have been associated with the concept of blackhole ; until now, nobody has detected gravitational waves. The essays contained in this book aim at showing that the concept of blackholes arises from a misinterpretation of general relativity and that gravitational waves cannot exist.

The focal image of the film "The BlackHole" functions as a visual metaphor for the sacred, order, unity, and eternal time. The blackhole is a symbol that unites the antinomic pairs of conscious/unconscious, water/fire, immersion/emersion, death/rebirth, and hell/heaven. The blackhole is further associated with the quest for…

Motivated by Maggiore's new interpretation of quasinormal modes, we investigate area spectra of a near extremal Schwarzschild-de Sitter blackhole and a higher-dimensional near extremal Reissner-Nordstrom-de Sitter blackhole. The result shows that the area spectra are equally spaced and irrelevant to the parameters of the blackholes. (orig.)

An explanation for the entropy of blackholes has been an outstanding problem in recent decades. A special case where this is possible is that of extremal blackholes in N=2 supergravity in four and five dimensions. The best developed case is for blackholes preserving some supersymmetry (BPS),

The effects of Wheeler’s quantum foam on blackhole growth are explored from an astrophysical per- spective. Quantum fluctuations in the form of mini (10−5 g) blackholes can couple to macroscopic blackholes and allow the latter to grow exponentially in mass on a time scale of 109 years.

The analytic structure of solutions to the Klein-Gordon equation in a blackhole background, as represented by monodromy data, is intimately related to blackhole thermodynamics. It encodes the "hidden conformal symmetry" of a nonextremal blackhole, and it explains why features of the inner event

loops [8]. In 1974, Hawking discovered that the blackholes emit thermal radiation due to quantum effects [9]. So the blackholes get evaporated depending upon their masses. Smaller the masses of the PBHs, quicker they evaporate. But the density of a blackhole varies inversely with its mass. So high density is needed for ...

In particular we pay attention to the effect of the expulsion of the ﬂux of external ﬁelds across charged and rotating blackholes which are approaching extremal states. Recently this effect has been shown to occur for blackhole solutions in string theory. We also discuss blackholes surrounded by rings and disks and rotating ...

The fuzzball proposal states that associated with a blackhole of entropy S, there are expS horizon-free non-singular solutions that asymptotically look like the blackhole but generically differ from the blackhole up to the horizon scale. These solutions, the fuzzballs, are considered to be the

Abstract. Primordial blackholes evaporate due to Hawking radiation. We find that the evaporation times of primordial blackholes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial blackholes are existing today, which strengthens the con- jecture that the primordial ...

Can we determine a spin parameter of a blackhole by observation of a blackhole shadow in an accretion disk? In order to answer this question, we make a qualitative analysis and a quantitative analysis of a shape and a position of a blackhole shadow casted by a rotating blackhole on an optically thick accretion disk and its dependence on an angular momentum of a blackhole. We have found blackhole shadows with a quite similar size and a shape for largely different blackhole spin paramete...

We review the recently established relationships between blackhole entropy in string theory and the quantum entanglement of qubits and qutrits in quantum information theory. The first example is provided by the measure of the tripartite entanglement of three qubits (Alice, Bob and Charlie), known as the 3-tangle, and the entropy of the 8-charge STU blackhole of N=2 supergravity, both of which are given by the [SL(2)]{sup 3} invariant hyperdeterminant, a quantity first introduced by Cayley in 1845. Moreover the classification of three-qubit entanglements is related to the classification of N=2 supersymmetric STU blackholes. There are further relationships between the attractor mechanism and local distillation protocols and between supersymmetry and the suppression of bit flip errors. At the microscopic level, the blackholes are described by intersecting D3-branes whose wrapping around the six compact dimensions T{sup 6} provides the string-theoretic interpretation of the charges and we associate the three-qubit basis vectors, |ABC>(A,B,C=0 or 1), with the corresponding 8 wrapping cycles. The blackhole/qubit correspondence extends to the 56 charge N=8 blackholes and the tripartite entanglement of seven qubits where the measure is provided by Cartan's E{sub 7} contains [SL(2)]{sup 7} invariant. The qubits are naturally described by the seven vertices ABCDEFG of the Fano plane, which provides the multiplication table of the seven imaginary octonions, reflecting the fact that E{sub 7} has a natural structure of an O-graded algebra. This in turn provides a novel imaginary octonionic interpretation of the 56=7x8 charges of N=8: the 24=3x8 NS-NS charges correspond to the three imaginary quaternions and the 32=4x8 R-R to the four complementary imaginary octonions. We contrast this approach with that based on Jordan algebras and the Freudenthal triple system. N=8 blackholes (or black strings) in five dimensions are also related to the bipartite entanglement of

We study phase transitions between blackholes with scalar hair and topological blackholes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ blackhole in three dimensions and topological blackhole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between blackhole with scalar hair (Martinez-Troncoso-Zanelli blackhole) and topological blackhole is second-order by using differences between two free energies. However, we do not identify what order of the phase transition between scalar and non-rotating BTZ blackholes occurs in three dimensions, although there exists a possible decay of scalar blackhole to non-rotating BTZ blackhole

Existing blackhole theory is found to be defective in its neglect of the physical properties of matter and radiation at superhigh densities. Nongravitational neutrino effects are shown to be physically relevant to the evolution of astronomical blackholes and their equations of state. Gravitational collapse to supernovae combined with the Davis and Ray vacuum solution for neutrinos limit attainment of a singularity and require blackholes to evolve into ''grey holes''. These allow a better justification than do blackholes for explaining the unique existence of galactic masses. (Auth.)

Supermassive blackholes have been discovered to grow more rapidly in young galaxy clusters, according to new results from NASA's Chandra X-ray Observatory. These "fast-track" supermassive blackholes can have a big influence on the galaxies and clusters that they live in. Using Chandra, scientists surveyed a sample of clusters and counted the fraction of galaxies with rapidly growing supermassive blackholes, known as active galactic nuclei (or AGN). The data show, for the first time, that younger, more distant galaxy clusters contained far more AGN than older, nearby ones. Galaxy clusters are some of the largest structures in the Universe, consisting of many individual galaxies, a few of which contain AGN. Earlier in the history of the universe, these galaxies contained a lot more gas for star formation and blackhole growth than galaxies in clusters do today. This fuel allows the young cluster blackholes to grow much more rapidly than their counterparts in nearby clusters. Illustration of Active Galactic Nucleus Illustration of Active Galactic Nucleus "The blackholes in these early clusters are like piranha in a very well-fed aquarium," said Jason Eastman of Ohio State University (OSU) and first author of this study. "It's not that they beat out each other for food, rather there was so much that all of the piranha were able to really thrive and grow quickly." The team used Chandra to determine the fraction of AGN in four different galaxy clusters at large distances, when the Universe was about 58% of its current age. Then they compared this value to the fraction found in more nearby clusters, those about 82% of the Universe's current age. The result was the more distant clusters contained about 20 times more AGN than the less distant sample. AGN outside clusters are also more common when the Universe is younger, but only by factors of two or three over the same age span. "It's been predicted that there would be fast-track blackholes in clusters, but we never

A modified formulation of the energy-momentum relation is proposed in the context of doubly special relativity. We investigate its impact on blackhole physics. It turns out that such a modification will give corrections to both the temperature and the entropy of blackholes. In particular, this modified dispersion relation also changes the picture of Hawking radiation greatly when the size of blackholes approaches the Planck scale. It can prevent blackholes from total evaporation, as a result providing a plausible mechanism to treat the remnant of blackholes as a candidate for dark matter

We study some features of the dyonic blackhole solution in heterotic string theory on a six-torus. This solution has 58 parameters. Of these, 28 parameters denote the electric charge of the blackhole, another 28 correspond to the magnetic charge, and the other two parameters are the mass and the angular momentum of the blackhole. We discuss the extremal limit and show that in various limits it reduces to the known blackhole solutions. The solutions saturating the Bogomolnyi bound are identified. An explicit solution is presented for the non-rotating dyonic blackhole. (orig.)

It is proven that the probability of a blackhole created from the de Sitter space-time background, at the Wkb level, is the exponential of one quarter of the sum of the blackhole and cosmological horizon areas, or the total entropy of the universe. This is true not only for the spherically symmetric cases of the Schwarzschild or Reissner-Nordstroem blackholes, but also for the rotating cases of the Kerr blackhole and the rotating charged case of the Newman blackhole. The de Sitter metric is the most probable evolution at the Planckian era of the universe.

We review some recently established connections between the mathematics of blackhole entropy in string theory and that of multipartite entanglement in quantum information theory. In the case of N=2 blackholes and the entanglement of three qubits, the quartic [SL(2)]^3 invariant, Cayley's hyperdeterminant, provides both the blackhole entropy and the measure of tripartite entanglement. In the case of N=8 blackholes and the entanglement of seven qubits, the quartic E_7 invariant of Cartan provides both the blackhole entropy and the measure of a particular tripartite entanglement encoded in the Fano plane.

This videotape is comprised of several segments of animations on blackholes and galaxy formation, and several segments of an interview with Dr. John Kormendy. The animation segments are: (1) a super massive blackhole, (2) Centarus A active blackhole found in a collision, (3) galaxy NGC-4261 (active blackhole and jet model), (4) galaxy M-32 (orbits of stars are effected by the gravity of the blackhole), (5) galaxy M-37 (motion of stars increases as mass of blackhole increases), (6) Birth of active galactic nuclei, (7) the collision of two galaxy leads to merger of the blackholes, (8) Centarus A and simulation of the collision of 2 galaxies. There are also several segments of an interview with John Kormendy. In these segments he discusses the two most important aspects of his recent blackhole work: (1) the correlations between galaxies speed and the mass of the blackholes, and (2) the existence of blackholes and galactic formation. He also discusses the importance of the Hubble Space Telescope and the Space Telescope Imaging Spectrograph to the study of blackholes. He also shows the methodology of processing images from the spectrograph in his office.

The stability of the Schwarzschild blackhole is studied. Using the Painlev\\'{e} coordinate, our region can be defined as the black-hole-connected region(r>2m, see text) of the Schwarzschild blackhole or the white-hole-connected region(r>2m, see text) of the Schwarzschild blackhole. We study the stable problems of the black-hole-connected region. The conclusions are: (1) in the black-hole-connected region, the initially regular perturbation fields must have real frequency or complex frequen...

We study analytically the relaxation phase of perturbed, rapidly rotating blackholes. In particular, we derive a simple formula for the fundamental quasinormal resonances of near-extremal Kerr blackholes. The formula is expressed in terms of the blackhole physical parameters: ω=mΩ-i2πT BH (n+(1/2)), where T BH and Ω are the temperature and angular velocity of the blackhole, and m is the azimuthal harmonic index of a corotating equatorial mode. This formula implies that the relaxation period τ∼1/ω of the blackhole becomes extremely long as the extremal limit T BH →0 is approached. The analytically derived formula is shown to agree with direct numerical computations of the blackhole resonances. We use our results to demonstrate analytically the fact that near-extremal Kerr blackholes saturate the recently proposed universal relaxation bound.

An effective field theory for infalling observers in the vicinity of a quasi-static blackhole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the blackhole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the blackhole more than a scrambling time earlier has been erased by the blackhole singularity. This property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the blackhole, ensures that a typical infalling observer does not encounter drama upon crossing the blackhole horizon in a theory where blackhole information is preserved for asymptotic observers.

An effective field theory for infalling observers in the vicinity of a quasi-static blackhole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the blackhole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the blackhole more than a scrambling time earlier has been erased by the blackhole singularity. This property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the blackhole, ensures that a typical infalling observer does not encounter drama upon crossing the blackhole horizon in a theory where blackhole information is preserved for asymptotic observers.

In this work, we investigate blackhole (BH) physics in the context of quantum corrections. These quantum corrections were introduced recently by replacing classical geodesics with quantal (Bohmian) trajectories and hence form a quantum Raychaudhuri equation (QRE). From the QRE, we derive a modified Schwarzschild metric, and use that metric to investigate BH singularity and thermodynamics. We find that these quantum corrections change the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. They prevent the BH from total evaporation, predicting the existence of a quantum BH remnant, which may introduce a possible resolution for the catastrophic behavior of Hawking radiation as the BH mass approaches zero. Those corrections also turn the spacelike singularity of the blackhole to be timelike, and hence this may ameliorate the information loss problem.

Full Text Available In this work, we investigate blackhole (BH physics in the context of quantum corrections. These quantum corrections were introduced recently by replacing classical geodesics with quantal (Bohmian trajectories and hence form a quantum Raychaudhuri equation (QRE. From the QRE, we derive a modified Schwarzschild metric, and use that metric to investigate BH singularity and thermodynamics. We find that these quantum corrections change the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. They prevent the BH from total evaporation, predicting the existence of a quantum BH remnant, which may introduce a possible resolution for the catastrophic behavior of Hawking radiation as the BH mass approaches zero. Those corrections also turn the spacelike singularity of the blackhole to be timelike, and hence this may ameliorate the information loss problem.

We study the constraints placed by quantum mechanics upon the lifetime of a blackhole. In the context of a moving-mirror analog model for the Hawking radiation process, we conclude that the period of Hawking radiation must be followed by a much longer period during which the remnant mass (of order m/sub P/) may be radiated away. We are able to place a lower bound on the time required for this radiation process, which translates into a lower bound for the lifetime of the blackhole. Particles which are emitted during the decay of the remnant, like the particles which comprise the Hawking flux, may be uncorrelated with each other. But each particle emitted from the decaying remnant is correlated with one particle emitted as Hawking radiation. The state which results after the remnant has evaporated is one which locally appears to be thermal, but which on a much larger scale is marked by extensive correlations

Middle cohomology states on the Higgs branch of supersymmetric quiver quantum mechanics - also known as pure Higgs states - have recently emerged as possible microscopic candidates for single-centered blackhole micro-states, as they carry zero angular momentum and appear to be robust under wall-crossing. Using the connection between quiver quantum mechanics on the Coulomb branch and the quantum mechanics of multi-centered blackholes, we propose a general algorithm for reconstructing the full moduli-dependent cohomology of the moduli space of an arbitrary quiver, in terms of the BPS invariants of the pure Higgs states. We analyze many examples of quivers with loops, including all cyclic Abelian quivers and several examples with two loops or non-Abelian gauge groups, and provide supporting evidence for this proposal. We also develop methods to count pure Higgs states directly.

We study magnetically charged classical solutions of a spontaneously broken gauge theory interacting with gravity. We show that nonsingular monopole solutions exist only if the Higgs field vacuum expectation value v is less than or equal to a critical value v sub cr, which is of the order of the Planck mass. In the limiting case, the monopole becomes a blackhole, with the region outside the horizon described by the critical Reissner-Nordstrom solution. For v less than v sub cr, we find additional solutions which are singular at f = 0, but which have this singularity hidden within a horizon. These have nontrivial matter fields outside the horizon, and may be interpreted as small blackholes lying within a magnetic monopole. The nature of these solutions as a function of v and of the total mass M and their relation to the Reissner-Nordstrom solutions is discussed.

An exact solution of Einstein's equations which represents a pair of accelerating and rotating blackholes (a generalized form of the spinning C-metric) is presented. The starting point is a form of the Plebanski-Demianski metric which, in addition to the usual parameters, explicitly includes parameters which describe the acceleration and angular velocity of the sources. This is transformed to a form which explicitly contains the known special cases for either rotating or accelerating blackholes. Electromagnetic charges and a NUT parameter are included, the relation between the NUT parameter l and the Plebanski-Demianski parameter n is given, and the physical meaning of all parameters is clarified. The possibility of finding an accelerating NUT solution is also discussed

Motivated by the fact that 2m/r is of the order of magnitude unity for the observable universe, we explore the possibility that a Schwarzschild or blackhole cosmological model is appropriate. Luminosity distance and frequency shifts of freely-falling, standard, monochromatic objects are viewed by a freely-falling observer. The observer is inside r=2m. The observer in such a world does not see the same universe as do astronomers. (author)

Full Text Available In the context of extended phase space, where the negative cosmological constant is treated as a thermodynamic pressure in the first law of blackhole thermodynamics, we find an asymptotically AdS metric whose thermodynamics matches exactly that of the Van der Waals fluid. We show that as a solution of Einstein's equations, the corresponding stress energy tensor obeys (at least for certain range of metric parameters all three weak, strong, and dominant energy conditions.

It has recently been shown that Bondi-van der Burg-Metzner-Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require blackholes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the blackhole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of blackholes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.

Full Text Available The entanglement entropy is a fundamental quantity, which characterizes the correlations between sub-systems in a larger quantum-mechanical system. For two sub-systems separated by a surface the entanglement entropy is proportional to the area of the surface and depends on the UV cutoff, which regulates the short-distance correlations. The geometrical nature of entanglement-entropy calculation is particularly intriguing when applied to blackholes when the entangling surface is the black-hole horizon. I review a variety of aspects of this calculation: the useful mathematical tools such as the geometry of spaces with conical singularities and the heat kernel method, the UV divergences in the entropy and their renormalization, the logarithmic terms in the entanglement entropy in four and six dimensions and their relation to the conformal anomalies. The focus in the review is on the systematic use of the conical singularity method. The relations to other known approaches such as ’t Hooft’s brick-wall model and the Euclidean path integral in the optical metric are discussed in detail. The puzzling behavior of the entanglement entropy due to fields, which non-minimally couple to gravity, is emphasized. The holographic description of the entanglement entropy of the black-hole horizon is illustrated on the two- and four-dimensional examples. Finally, I examine the possibility to interpret the Bekenstein-Hawking entropy entirely as the entanglement entropy.

We present a physically motivated derivation of the JWKB backward glory-scattering cross section of massless waves by Schwarzschild blackholes. The angular dependence of the cross section is identical with the one derived by path integration, namely, dsigma/dΩ = 4π 2 lambda -1 B/sub g/ 2 (dB mWπ, where lambda is the wavelength, B(theta) is the inverse of the classical deflection function CTHETA(B), B/sub g/ is the glory impact parameter, s is the helicity of the scattered wave, and J/sub 2s/ is the Bessel function of order 2s. The glory rings formed by scalar waves are bright at the center; those formed by polarized waves are dark at the center. For scattering of massless particles by a spherical blackhole of mass M, B(theta)/Mapprox.3 √3 + 3.48 exp(-theta), theta > owigπ. The numerical values of dsigma/dΩ for this deflection function are found to agree with earlier computer calculations of glory cross sections from blackholes

NASA has begun examining the technologies needed for an Interstellar Mission. In 1998, a NASA Interstellar Mission Workshop was held at the California Institute of Technology to examine the technologies required. Since then, a spectrum of research efforts to support such a mission has been underway, including many advanced and futuristic space propulsion concepts which are being explored. The study of blackholes and wormholes may provide some of the breakthrough physics needed to travel to the stars. The first blackhole, CYGXI, was discovered in 1972 in the constellation Cygnus X-1. In 1993, a blackhole was found in the center of our Milky Way Galaxy. In 1994, the blackhole GRO J1655-40 was discovered by the NASA Marshall Space Flight center using the Gamma Ray Observatory. Today, we believe we have found evidence to support the existence of 19 blackholes, but our universe may contain several thousands. This paper discusses the dead star states - - both stable and unstable, white dwarfs, neutron stars, pulsars, quasars, the basic features and types of blackholes: nonspinning, nonspinning with charge, spinning, and Hawking's mini blackholes. The search for blackholes, gravitational waves, and Laser Interferometer Gravitational Wave Observatory (LIGO) are reviewed. Finally, concepts of blackhole powered space vehicles and wormhole concepts for rapid interstellar travel are discussed in relation to the NASA Interstellar Mission.

A wave impinging on a Kerr blackhole can be amplified as it scatters off the hole if certain conditions are satisfied, giving rise to superradiant scattering. By placing a mirror around the blackhole one can make the system unstable. This is the black-hole bomb of Press and Teukolsky. We investigate in detail this process and compute the growing time scales and oscillation frequencies as a function of the mirror's location. It is found that in order for the system blackhole plus mirror to become unstable there is a minimum distance at which the mirror must be located. We also give an explicit example showing that such a bomb can be built. In addition, our arguments enable us to justify why large Kerr-AdS blackholes are stable and small Kerr-AdS blackholes should be unstable

We use the analytic continuation procedure proposed in our earlier works to study the thermodynamics of blackholes in 2 + 1 dimensions. A general blackhole in 2 + 1 dimensions has g handles hidden behind h horizons. The result of the analytic continuation of a black-hole spacetime is a hyperbolic 3-manifold having the topology of a handlebody. The boundary of this handlebody is a compact Riemann surface of genus G = 2g + h - 1. Conformal moduli of this surface encode in a simple way the physical characteristics of the blackhole. The moduli space of blackholes of a given type (g, h) is then the Schottky space at genus G. The (logarithm of the) thermodynamic partition function of the hole is the Kaehler potential for the Weil-Peterson metric on the Schottky space. The Bekenstein bound on the black-hole entropy leads us to conjecture a new strong bound on this Kaehler potential

It is shown that the strong gravity theory of Salam et al. places severe restrictions on blackhole evaporation. Two major implications are that: mini blck holes (down to masses approximately 10 -16 kg) would be stable in the present epoch; and that some suggested mini blackhole mechanisms to explain astrophysical phenomena would not work. The first result implies that f-gravity appears to make blackholes much safer by removing the possibility of extremely violent blackhole explosions suggested by Hawking. (Auth.)

In the following paper, certain blackhole dynamic potentials have been ... the equations of the laws of blackhole dynamics as given by Bekenstein and those ..... work. This makes K, the energy which is available for work in time-reversible pro- cesses (white holes) observing constancy of surface gravity. Since the area of the.

It has recently been pointed out that the spinning Kerr blackhole with maximal spin could act as a particle collider with arbitrarily high center-of-mass energy. In this paper, we will extend the result to the charged spinning blackhole, the Kerr-Newman blackhole. The center-of-mass energy of collision for two uncharged particles falling freely from rest at infinity depends not only on the spin a but also on the charge Q of the blackhole. We find that an unlimited center-of-mass energy can be approached with the conditions: (1) the collision takes place at the horizon of an extremal blackhole; (2) one of the colliding particles has critical angular momentum; (3) the spin a of the extremal blackhole satisfies (1/√(3))≤(a/M)≤1, where M is the mass of the Kerr-Newman blackhole. The third condition implies that to obtain an arbitrarily high energy, the extremal Kerr-Newman blackhole must have a large value of spin, which is a significant difference between the Kerr and Kerr-Newman blackholes. Furthermore, we also show that, for a near-extremal blackhole, there always exists a finite upper bound for center-of-mass energy, which decreases with the increase of the charge Q.

An introductory approach to blackholes is presented along with astronomical observational data pertaining to the presence of a supermassive blackhole at the center of our galaxy. Concepts of conservation of energy and Kepler's third law are employed so students can apply formulas from their physics class to determine the mass of the black hole…

In this paper, we study the BSW process of the slowly evaporating charged blackhole. It can be found that the BSW process will also arise near blackhole horizon when the evaporation of charged blackhole is very slow. But now the background blackhole does not have to be an extremal blackhole, and it will be approximately an extremal blackhole unless it is nearly a huge stationary blackhole.

The most promising way of detecting blackholes seems to be through electromagnetic radiation emitted by nearby charged particles. The nature of this radiation depends strongly on the local electromagnetic field, which varies with the charge of the blackhole. It has often been purported that a blackhole with significant charge will not be observed, because, the dominance of the Coulomb interaction forces its neutralization through selective accretion. This paper shows that it is possible to balance the electric attraction of particles whose charge is opposite that of the blackhole with magnetic forces and (assuming an axisymmetric, stationary solution) covariantly define the regions in which this is possible. A Kerr-Newman hole in an asymptotically uniform magnetic field and a current ring centered about a Reissner-Nordstroem hole are used as examples, because of their relevance to processes through which blackholes may be observed. (Auth.)

The extraction of rotational energy from a spinning blackhole via the Blandford-Znajek mechanism has long been understood as an important component in models to explain energetic jets from compact astrophysical sources. Here we show more generally that the kinetic energy of the blackhole, both rotational and translational, can be tapped, thereby producing even more luminous jets powered by the interaction of the blackhole with its surrounding plasma. We study the resulting Poynting jet that arises from single boosted blackholes and binary blackhole systems. In the latter case, we find that increasing the orbital angular momenta of the system and/or the spins of the individual blackholes results in an enhanced Poynting flux.

TeV-scale gravity theories allow the possibility of producing small blackholes at energies that soon will be explored at the CERN LHC or at the Auger observatory. One of the expected signatures is the detection of Hawking radiation that might eventually terminate if the blackhole, once perturbed, leaves the brane. Here, we study how the 'blackhole plus brane' system evolves once the blackhole is given an initial velocity that mimics, for instance, the recoil due to the emission of a graviton. The results of our dynamical analysis show that the brane bends around the blackhole, suggesting that the blackhole eventually escapes into the extra dimensions once two portions of the brane come in contact and reconnect. This gives a dynamical mechanism for the creation of baby branes

We study the hidden conformal symmetry of extremal blackholes. We introduce a new set of conformal coordinates to write the SL(2,R) generators. We find that the Laplacian of the scalar field in many extremal blackholes, including Kerr(-Newman), Reissner-Nordstrom, warped AdS 3 , and null warped blackholes, could be written in terms of the SL(2,R) quadratic Casimir. This suggests that there exist dual conformal field theory (CFT) descriptions of these blackholes. From the conformal coordinates, the temperatures of the dual CFTs could be read directly. For the extremal blackhole, the Hawking temperature is vanishing. Correspondingly, only the left (right) temperature of the dual CFT is nonvanishing, and the excitations of the other sector are suppressed. In the probe limit, we compute the scattering amplitudes of the scalar off the extremal blackholes and find perfect agreement with the CFT prediction.

Building upon our previous work on two-dimensional stringy blackholes and its extension to spherically-symmetric four-dimensional stringy blackholes, we show how the latter retain information. A key r\\^ole is played by an infinite-dimensional $W_\\infty$ symmetry that preserves the area of an isolated black-hole horizon and hence its entropy. The exactly-marginal conformal world-sheet operator representing a massless stringy particle interacting with the blackhole necessarily includes a contribution from $W_\\infty$ generators in its vertex function. This admixture manifests the transfer of information between the string blackhole and external particles. We discuss different manifestations of $W_\\infty$ symmetry in black-hole physics and the connections between them.

We present a new model for the formation of blackholes in cosmological simulations, motivated by the first star formation. Blackholes form from high density peaks of primordial gas, and grow via both gas accretion and mergers. Massive blackholes heat the surrounding material, suppressing star formation at the centres of galaxies, and driving galactic winds. We perform an investigation into the physical effects of the model parameters, and obtain a `best' set of these parameters by comparing the outcome of simulations to observations. With this best set, we successfully reproduce the cosmic star formation rate history, blackhole mass-velocity dispersion relation, and the size-velocity dispersion relation of galaxies. The blackhole seed mass is ˜103 M⊙, which is orders of magnitude smaller than that which has been used in previous cosmological simulations with active galactic nuclei, but suggests that the origin of the seed blackholes is the death of Population III stars.

Emitting no radiation or any other kind of information, blackholes mark the edge of the universe--both physically and in our scientific understanding. Yet astronomers have found clear evidence for the existence of blackholes, employing the same tools and techniques used to explore other celestial objects. In this sophisticated introduction, leading astronomer Charles Bailyn goes behind the theory and physics of blackholes to describe how astronomers are observing these enigmatic objects and developing a remarkably detailed picture of what they look like and how they interact with their surroundings. Accessible to undergraduates and others with some knowledge of introductory college-level physics, this book presents the techniques used to identify and measure the mass and spin of celestial blackholes. These key measurements demonstrate the existence of two kinds of blackholes, those with masses a few times that of a typical star, and those with masses comparable to whole galaxies--supermassive blackholes...

I examine the pair creation of blackholes in space-times with a cosmological constant of either sign. I consider cosmological C-metrics and show that the conical singularities in this metric vanish only for three distinct classes of blackhole metric, two of which have compact event horizons on each spatial slice. One class is a generalization of the Reissner-Nordstroem (anti-)de Sitter blackholes in which the event horizons are the direct product of a null line with a 2-surface with topology of genus g. The other class consists of neutral blackholes whose event horizons are the direct product of a null conoid with a circle. In the presence of a domain wall, blackhole pairs of all possible types will be pair created for a wide range of mass and charge, including even negative mass blackholes. I determine the relevant instantons and Euclidean actions for each case. (orig.)

A Carnot cycle outside a Schwarzschild blackhole is investigated in detail. We propose a reversible Carnot cycle with a blackhole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature T 1 and a blackhole with Hawking temperature T H . By naturally extending the ordinary Carnot cycle to the blackhole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1 – T H /T 1 . Consequently, blackholes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the blackhole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible. (general)

The constant curvature (CC) blackholes are higher dimensional generalizations of Banados-Teitelboim-Zanelli blackholes. It is known that these blackholes have the unusual topology of M D-1 xS 1 , where D is the spacetime dimension and M D-1 stands for a conformal Minkowski spacetime in D-1 dimensions. The unusual topology and time-dependence for the exterior of these blackholes cause some difficulties to derive their thermodynamic quantities. In this work, by using a globally embedding approach, we obtain the Hawking temperature of the CC blackholes. We find that the Hawking temperature takes the same form when using both the static and global coordinates. Also, it is identical to the Gibbons-Hawking temperature of the boundary de Sitter spaces of these CC blackholes.

The superradiant scattering of massive scalar particles by a rotating mini blackhole is investigated. Imposing the mirror boundary condition, the system becomes the so called black-hole bomb where the rotation energy of the blackhole is transferred to the scattered particle exponentially with time. Bulk emissions as well as brane emissions are considered altogether. It is found that the largest effects are expected for the brane emission of lower angular modes with lighter mass and larger a...

We study the thermodynamics and geometrothermodynamics of different blackhole configurations in more than four spacetime dimensions. We use the response functions to find the conditions under which second order phase transitions occur in higher-dimensional static Reissner-Nordström and stationary Kerr blackholes. Our results indicate that the equilibrium manifold of all these blackhole configurations is in general curved and that curvature singularities appear exactly at those places where second order phase transitions occur.

We start by pointing out that certain Riemann surfaces appear rather naturally in the context of wave equations in the blackhole background. For a given blackhole there are two closely related surfaces. One is the Riemann surface of complexified ``tortoise'' coordinate. The other Riemann surface appears when the radial wave equation is interpreted as the Fuchsian differential equation. We study these surfaces in detail for the BTZ and Schwarzschild blackholes in four and higher dimensions....

We analyze terms subleading to Rutherford in the $S$-matrix between blackhole and probes of successively high energies. We show that by an appropriate choice of the probe one can read off the quantum state of the blackhole from the S-matrix, staying asymptotically far from the BH all the time. We interpret the scattering experiment as scattering off classical stringy backgrounds which explicitly depend on the internal quantum numbers of the blackhole.

Mergers of black-hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates too low to be of observational interest. In this paper we explore the possibility that blackholes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, blackholes become the most massive objects within a few tens of millions of years; dynamical relaxation...

Full Text Available The formation of a blackhole and its event horizon are described. Conclusions, which are the result of a thought experiment, show that Schwarzschild [1] was correct: A singularity develops at the event horizon of a newly-formed blackhole. The intense gravitational field that forms near the event horizon results in the mass-energy of the blackhole accumulating in a layer just inside the event horizon, rather than collapsing into a central singularity.

In this article we study gravitational lensing by non-rotating and asymptotically flat blackholes in Horndeski theory. By adopting the strong deflection limit, we calculate the deflection angle, from which we obtain the positions and the magnifications of the relativistic images. We compare our results with those corresponding to blackholes in General Relativity. We analyze the astrophysical consequences in the case of the nearest supermassive blackholes. (orig.)

In the space of thermodynamic equilibrium states we introduce a Legendre invariant metric which contains all the information about the thermodynamics of blackholes. The curvature of this thermodynamic metric becomes singular at those points where, according to the analysis of the heat capacities, phase transitions occur. This result is valid for the Kerr-Newman blackhole and all its special cases and, therefore, provides a unified description of blackhole phase transitions in terms of curvature singularities.

A typical galaxy is thought to contain tens of millions of stellar-mass blackholes, the collapsed remnants of once massive stars, and a single nuclear supermassive blackhole. Both classes of blackholes accrete gas from their environments. The accreting gas forms a flattened orbiting structure known as an accretion disk. During the past several years, it has become possible to obtain measurements of the spins of the two classes of blackholes by modeling the x-ray emission from their accretion disks. Two methods are employed, both of which depend upon identifying the inner radius of the accretion disk with the innermost stable circular orbit, whose radius depends only on the mass and spin of the blackhole. In the Fe Kα method, which applies to both classes of blackholes, one models the profile of the relativistically broadened iron line with a special focus on the gravitationally redshifted red wing of the line. In the continuum-fitting (CF) method, which has so far only been applied to stellar-mass blackholes, one models the thermal x-ray continuum spectrum of the accretion disk. We discuss both methods, with a strong emphasis on the CF method and its application to stellar-mass blackholes. Spin results for eight stellar-mass blackholes are summarized. These data are used to argue that the high spins of at least some of these blackholes are natal, and that the presence or absence of relativistic jets in accreting blackholes is not entirely determined by the spin of the blackhole.

How many blackholes lurk within the dense environments of globular clusters, and how do these powerful objects shape the properties of the cluster around them? One such cluster, NGC 3201, is now helping us to answer these questions.Hunting Stellar-Mass BlackHolesSince the detection of merging black-hole binaries by the Laser Interferometer Gravitational-Wave Observatory (LIGO), the dense environments of globular clusters have received increasing attention as potential birthplaces of these compact binary systems.The central region of the globular star cluster NGC 3201, as viewed by Hubble. The blackhole is in orbit with the star marked by the blue circle. [NASA/ESA]In addition, more and more stellar-mass black-hole candidates have been observed within globular clusters, lurking in binary pairs with luminous, non-compact companions. The most recent of these detections, found in the globular cluster NGC 3201, stands alone as the first stellar-mass blackhole candidate discovered via radial velocity observations: the blackholes main-sequence companion gave away its presence via a telltale wobble.Now a team of scientists led by Kyle Kremer (CIERA and Northwestern University) is using models of this system to better understand the impact that blackholes might have on their host clusters.A Model ClusterThe relationship between blackholes and their host clusters is complicated. Though the cluster environment can determine the dynamical evolution of the blackholes, the retention rate of blackholes in a globular cluster (i.e., how many remain in the cluster when they are born as supernovae, rather than being kicked out during the explosion) influences how the host cluster evolves.Kremer and collaborators track this complex relationship by modeling the evolution of a cluster similar to NGC 3201 with a Monte Carlo code. The code incorporates physics relevant to the evolution of blackholes and black-hole binaries in globular clusters, such as two-body relaxation

These lectures give an elementary introduction to the subject of four dimensional blackholes (BHs) in supergravity and the Attractor Mechanism in the extremal case. Some thermodynamical properties are discussed and some relevant formula for the critical points of the BH effective potential are given. The case of Maxwell-Einstein-axion-dilaton (super)gravity is discussed in detail. Analogies among BH entropy and multipartite entanglement of qubits in quantum information theory, as well moduli spaces of extremal BH attractors, are also discussed.

Bridging the gap between the approximately ten solar mass 'stellar mass' blackholes and the 'supermassive' blackholes of millions to billions of solar masses are the elusive 'intermediate-mass' blackholes. Their discovery is key to understanding whether supermassive blackholes can grow from stellar-mass blackholes or whether a more exotic process accelerated their growth soon after the Big Bang. Currently, tentative evidence suggests that the progenitors of supermassive blackholes were formed as ∼10(4)-10(5) M(⊙) blackholes via the direct collapse of gas. Ongoing searches for intermediate-mass blackholes at galaxy centres will help shed light on this formation mechanism.

The fate of quantum entanglement interacting with a blackhole has been an enduring mystery, not the least because standard curved space field theory does not address the interaction of blackholes with matter. We discuss an effective Hamiltonian of matter interacting with a blackhole that has a precise analogue in quantum optics and correctly reproduces both spontaneous and stimulated Hawking radiation with grey-body factors. We calculate the quantum capacity of this channel in the limit of perfect absorption, as well as in the limit of a perfectly reflecting blackhole (a white hole). We find that the white hole is an optimal quantum cloner, and is isomorphic to the Unruh channel with positive quantum capacity. The complementary channel (across the horizon) is entanglement-breaking with zero capacity, avoiding a violation of the quantum no-cloning theorem. The blackhole channel on the contrary has vanishing capacity, while its complement has positive capacity instead. Thus, quantum states can be reconstructed faithfully behind the blackhole horizon, but not outside. This work sheds new light on blackhole complementarity because it shows that blackholes can both reflect and absorb quantum states without violating the no-cloning theorem, and makes quantum firewalls obsolete.

We investigate the thermodynamics of a general class of exact 4-dimensional asymptotically Anti-de Sitter hairy blackhole solutions and show that, for a fixed temperature, there are small and large hairy blackholes similar to the Schwarzschild–AdS blackhole. The large blackholes have positive specific heat and so they can be in equilibrium with a thermal bath of radiation at the Hawking temperature. The relevant thermodynamic quantities are computed by using the Hamiltonian formalism and counterterm method. We explicitly show that there are first order phase transitions similar to the Hawking–Page phase transition.

We study the formation and the evaporation of a spherically symmetric blackhole in conformal gravity. From the collapse of a spherically symmetric thin shell of radiation, we find a singularity-free non-rotating blackhole. This blackhole has the same Hawking temperature as a Schwarzschild blackhole with the same mass, and it completely evaporates either in a finite or in an infinite time, depending on the ensemble. We consider the analysis both in the canonical and in the micro-canonical statistical ensembles. Last, we discuss the corresponding Penrose diagram of this physical process.

Unitarity implies that the evaporation of microscopic quasiclassical blackholes cannot be universal in different particle species. This creates a puzzle, since it conflicts with the thermal nature of quasiclassical blackholes, according to which all of the species should see the same horizon and be produced with the same Hawking temperatures. We resolve this puzzle by showing that for the microscopic blackholes, on top of the usual quantum evaporation time, there is a new time scale which characterizes a purely classical process during which the blackhole loses the ability to differentiate among the species and becomes democratic. We demonstrate this phenomenon in a well-understood framework of large extra dimensions, with a number of parallel branes. An initially nondemocratic blackhole is the one localized on one of the branes, with its high-dimensional Schwarzschild radius being much shorter than the interbrane distance. Such a blackhole seemingly cannot evaporate into the species localized on the other branes that are beyond its reach. We demonstrate that in reality the system evolves classically in time, in such a way that the blackhole accretes the neighboring branes. The end result is a completely democratic static configuration, in which all of the branes share the same blackhole and all of the species are produced with the same Hawking temperature. Thus, just like their macroscopic counterparts, the microscopic blackholes are universal bridges to the hidden sector physics.

Considering blackhole as spacetime and slightly modifying the big bang theory, the author has recently developed a new cosmological model called blackhole universe, which is consistent with Mach principle and Einsteinian general relativity and self consistently explains various observations of the universe without difficulties. According to this model, the universe originated from a hot star-like blackhole and gradually grew through a supermassive blackhole to the present universe by accreting ambient material and merging with other blackholes. The entire space is infinitely and hierarchically layered and evolves iteratively. The innermost three layers are the universe that we lives, the outside space called mother universe, and the inside star-like and supermassive blackholes called child universes. The outermost layer has an infinite radius and zero limits for both the mass density and absolute temperature. All layers or universes are governed by the same physics, the Einstein general relativity with the Robertson-Walker metric of spacetime, and tend to expand outward physically. When one universe expands out, a new similar universe grows up from its inside blackholes. The origin, structure, evolution, expansion, and cosmic microwave background radiation of blackhole universe have been presented in the recent sequence of American Astronomical Society (AAS) meetings and published in peer-review journals. This study will show how this new model explains the acceleration of the universe and why dark energy is not required. We will also compare the blackhole universe model with the big bang cosmology.

In the classical relativistic regime, the accretion of phantom-like dark energy onto a stationary blackhole reduces the mass of the blackhole. We have investigated the accretion of phantom energy onto a stationary charged blackhole and have determined the condition under which this accretion is possible. This condition restricts the mass-to-charge ratio in a narrow range. This condition also challenges the validity of the cosmic-censorship conjecture since a naked singularity is eventually produced due to accretion of phantom energy onto blackhole. (orig.)

If a blackhole can accrete a body whose spin or charge would send the blackhole parameters over the extremal limit, then a naked singularity would presumably form, in violation of the cosmic censorship conjecture. We review some previous results on testing cosmic censorship in this way using the test body approximation, focusing mostly on the case of neutral blackholes. Under certain conditions a blackhole can indeed be over-spun or over-charged in this approximation, hence radiative and self-force effects must be taken into account to further test cosmic censorship.

Quantum effects imply that an infalling observer cannot cross the event horizon of an evaporating blackhole, even in her proper time. The Penrose diagram of an evaporating blackhole is different from the one usually reported in the literature. We show that before the observer can cross the horizon the blackhole disappears. Possible observational consequences are discussed. - Highlights: • We calculate the in-falling light geodesics in an evaporating blackhole. • For our calculation we use a non-static metric called Vaydia metric. • We show that in-falling light cannot cross the event horizon. • In this case there is no information paradox.

Based on the latest public results, 13 TeV data from the Large Hadron Collider at CERN has not indicated any evidence of hitherto tested models of quantum blackholes, semiclassical blackholes, or string balls. Such models have predicted signatures of particles with high transverse momenta. Noncommutative blackholes remain an untested model of TeV-scale gravity that offers the starkly different signature of particles with relatively low transverse momenta. Considerations for a search for charged noncommutative blackholes using the ATLAS detector will be discussed.

The tidal deformation of an extended test body falling with zero angular momentum into a Kerr blackhole is calculated. Numerical results for infall along the symmetry axis and in the equatorial plane of the blackhole are presented for a range of values of a, the specific angular momentum of the blackhole. Estimates of the tidal contribution to the gravitational radiation are also given. The tidal contribution in equatorial infall into a maximally rotating Kerr blackhole may be of the same order as the center-of-mass contribution to the gravitational radiation

On the basis of the Kerr metric as a model for a spinning blackhole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows not only that classical blackholes are internally unstable, but also that Planck-scale physics is a characteristic feature within blackholes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for blackholes with rotation, and in this sense it is distinct from the well-known Cauchy horizon instability.

We study the evolution of a massive scalar field surrounding a Schwarzschild blackhole and find configurations that can survive for arbitrarily long times, provided the blackhole or the scalar field mass is small enough. In particular, both ultralight scalar field dark matter around supermassive blackholes and axionlike scalar fields around primordial blackholes can survive for cosmological times. Moreover, these results are quite generic in the sense that fairly arbitrary initial data evolve, at late times, as a combination of those long-lived configurations.

In this work, we consider the fluid/gravity correspondence for general rotating blackholes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating blackholes contains a Coriolis force term, which is closely related to the angular velocity of the blackhole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating blackhole under the holographic picture.

Full Text Available In this work, we consider the fluid/gravity correspondence for general rotating blackholes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating blackholes contains a Coriolis force term, which is closely related to the angular velocity of the blackhole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating blackhole under the holographic picture.

We investigate the behavior of low-mass, planar domain walls in the so-called ϕ4 model of the scalar field on the Schwarzschild and Kerr backgrounds. We focus on a transit of a domain wall through a blackhole and solve numerically the equations of motion for a range of parameters of the domain wall and the blackhole. We observe a behavior resembling an occurrence of ringing modes. Perturbations of domain walls vanish during latter evolution, suggesting their stability against a passage through the blackhole. The results obtained for Kerr and Reissner-Nordström blackholes are also compared.

It is shown that the entropy of the radiation evaporated by an uncharged, nonrotating blackhole into vacuum in the course of its lifetime is approximately (4/3) times the initial entropy of this blackhole. Also considered is a thermodynamically reversible process in which an increase of black-hole entropy is equal to the decrease of the entropy of its surroundings. Implications of these results for the generalized second law of thermodynamics and for the interpretation of black-hole entropy are pointed out

Blackhole complementarity is incompatible with the existence of traversable wormholes. In fact, traversable wormholes cause problems for any theory where information comes out in the Hawking radiation.

To explain blackhole thermodynamics in quantum gravity, one must introduce constraints to ensure that a blackhole is actually present. I show that for a large class of blackholes, such "horizon constraints" allow the use of conformal field theory techniques to compute the density of states, reproducing the Bekenstein-Hawking entropy in a nearly model-independent manner. One standard string theory approach to blackhole entropy arises as a special case, lending support to the claim that the mechanism may be "universal." I argue that the relevant degrees of freedom are Goldstone-boson-like excitations arising from the weak breaking of symmetry by the constraints.

In this paper we are trying to explain our point of view on what a quantum blackhole is. The ideas are based on the previous works by the author and his collaborators where the concrete models of quantum blackholes were constructed. It is argued that the main feature of quantum blackholes that would allow us to distinguish them from other quantum object is some specific quantum radiation. Such a radiation in the quasiclassical limit is just the Hawking evaporation if the change in the blackhole mass due to radiation can be neglected

The Raychaudhuri equation is used to analyze the effect of the Hawking radiation back reaction upon a black-hole event horizon. It is found that if the effective stress-energy tensor of the Hawking radiation has negative energy density as expected, then an evaporating blackhole initially a solar mass in size must disappear in less than a second. This implies that either the evaporation process, if it occurs at all, must be quite different from what is commonly supposed, or else black-hole event horizons: and hence blackholes: do not exist

Algebraically special perturbations of blackholes excite gravitational waves that are either purely ingoing or purely outgoing. Solutions, appropriate to such perturbations of the Kerr, the Schwarzschild, and the Reissner-Nordstroem black-holes, are obtained in explicit forms by different methods. The different methods illustrate the remarkable inner relations among different facets of the mathematical theory. In the context of the Kerr black-hole they derive from the different ways in which the explicit value of the Starobinsky constant emerges, and in the context of the Schwarzschild and the Reissner-Nordstroem black-holes they derive from the potential barriers surrounding them belonging to a special class. (author)

The very largest blackholes reach a certain point and then grow no more, according to the best survey to date of blackholes made with NASA's Chandra X-ray Observatory. Scientists have also discovered many previously hidden blackholes that are well below their weight limit. These new results corroborate recent theoretical work about how blackholes and galaxies grow. The biggest blackholes, those with at least 100 million times the mass of the Sun, ate voraciously during the early Universe. Nearly all of them ran out of 'food' billions of years ago and went onto a forced starvation diet. Focus on BlackHoles in the Chandra Deep Field North Focus on BlackHoles in the Chandra Deep Field North On the other hand, blackholes between about 10 and 100 million solar masses followed a more controlled eating plan. Because they took smaller portions of their meals of gas and dust, they continue growing today. "Our data show that some supermassive blackholes seem to binge, while others prefer to graze", said Amy Barger of the University of Wisconsin in Madison and the University of Hawaii, lead author of the paper describing the results in the latest issue of The Astronomical Journal (Feb 2005). "We now understand better than ever before how supermassive blackholes grow." One revelation is that there is a strong connection between the growth of blackholes and the birth of stars. Previously, astronomers had done careful studies of the birthrate of stars in galaxies, but didn't know as much about the blackholes at their centers. DSS Optical Image of Lockman Hole DSS Optical Image of Lockman Hole "These galaxies lose material into their central blackholes at the same time that they make their stars," said Barger. "So whatever mechanism governs star formation in galaxies also governs blackhole growth." Astronomers have made an accurate census of both the biggest, active blackholes in the distance, and the relatively smaller, calmer ones closer by. Now, for the first

We discuss geometrical properties of the horizon surface of five-dimensional rotating blackholes and black rings. Geometrical invariants characterizing these 3D geometries are calculated. We obtain a global embedding of the 5D rotating black horizon surface into a flat space. We also describe the Kaluza-Klein reduction of the black ring solution (along the direction of its rotation) which, though it is nakedly singular, relates this solution to the 4D metric of a static blackhole distorted by the presence of external scalar (dilaton) and vector ('electromagnetic') fields. The properties of the reduced blackhole horizon and its embedding in E 3 are briefly discussed

Fluid discs and tori around blackholes are discussed within different approaches and with the emphasis on the role of disc gravity. First reviewed are the prospects of investigating the gravitational field of a blackhole-disc system using analytical solutions of stationary, axially symmetric Einstein equations. Then, more detailed considerations are focused to the middle and outer parts of extended disc-like configurations where relativistic effects are small and the Newtonian description is adequate. Within general relativity, only a static case has been analysed in detail. Results are often very inspiring. However, simplifying assumptions must be imposed: ad hoc profiles of the disc density are commonly assumed and the effects of frame-dragging are completely lacking. Astrophysical discs (e.g. accretion discs in active galactic nuclei) typically extend far beyond the relativistic domain and are fairly diluted. However, self-gravity is still essential for their structure and evolution, as well as for their radiation emission and the impact on the surrounding environment. For example, a nuclear star cluster in a galactic centre may bear various imprints of mutual star-disc interactions, which can be recognized in observational properties, such as the relation between the central mass and stellar velocity dispersion. (topical review)

Under the assumption that a UV theory does not display superluminal behavior, we ask what constraints on superluminality are satisfied in the effective field theory (EFT). We study two examples of effective theories: quantum electrodynamics (QED) coupled to gravity after the electron is integrated out, and the flat-space galileon. The first is realized in nature, the second is more speculative, but they both exhibit apparent superluminality around non-trivial backgrounds. In the QED case, we attempt, and fail, to find backgrounds for which the superluminal signal advance can be made larger than the putative resolving power of the EFT. In contrast, in the galileon case it is easy to find such backgrounds, indicating that if the UV completion of the galileon is (sub)luminal, quantum corrections must become important at distance scales of order the Vainshtein radius of the background configuration, much larger than the naive EFT strong coupling distance scale. Such corrections would be reminiscent of the non-perturbative Schwarzschild scale quantum effects that are expected to resolve the blackhole information problem. Finally, a byproduct of our analysis is a calculation of how perturbative quantum effects alter charged Reissner-Nordstrom blackholes.

Many condensed matter experiments explore the finite temperature dynamics of systems near quantum critical points. Often, there are no well-defined quasiparticle excitations, and so quantum kinetic equations do not describe the transport properties completely. The theory shows that the transport coefficients are not proportional to a mean free scattering time (as is the case in the Boltzmann theory of quasiparticles), but are completely determined by the absolute temperature and by equilibrium thermodynamic observables. Recently, explicit solutions of this quantum critical dynamics have become possible via the anti-de Sitter/conformal field theory duality discovered in string theory. This shows that the quantum critical theory provides a holographic description of the quantum theory of blackholes in a negatively curved anti-de Sitter space, and relates its transport coefficients to properties of the Hawking radiation from the blackhole. We review how insights from this connection have led to new results for experimental systems: (i) the vicinity of the superfluid-insulator transition in the presence of an applied magnetic field, and its possible application to measurements of the Nernst effect in the cuprates, (ii) the magnetohydrodynamics of the plasma of Dirac electrons in graphene and the prediction of a hydrodynamic cyclotron resonance.

If blackholes were able to clone quantum states, a number of paradoxes in blackhole physics would disappear. However, the linearity of quantum mechanics forbids exact cloning of quantum states. Here we show that blackholes indeed clone incoming quantum states with a fidelity that depends on the black hole’s absorption coefficient, without violating the no-cloning theorem because the clones are only approximate. Perfectly reflecting blackholes are optimal universal ‘quantum cloning machines’ and operate on the principle of stimulated emission, exactly as their quantum optical counterparts. In the limit of perfect absorption, the fidelity of clones is only equal to what can be obtained via quantum state estimation methods. But for any absorption probability less than one, the cloning fidelity is nearly optimal as long as ω /T≥slant 10, a common parameter for modest-sized blackholes.

We consider a class of Einstein-Maxwell-Dilaton theories, in which the dilaton coupling to the Maxwell field is not the usual single exponential function, but one with a stationary point. The theories admit two charged blackholes: one is the Reissner-Nordstrøm (RN) blackhole and the other has a varying dilaton. For a given charge, the new blackhole in the extremal limit has the same AdS{sub 2}×Sphere near-horizon geometry as the RN blackhole, but it carries larger mass. We then introduce some scalar potentials and obtain exact charged AdS blackholes. We also generalize the results to black p-branes with scalar hair.

We find multiple relations between extremal blackholes in string theory and 2- and 3-qubit systems in quantum information theory. We show that the entropy of the axion-dilaton extremal blackhole is related to the concurrence of a 2-qubit state, whereas the entropy of the STU blackholes, Bogomol'nyi-Prasad-Sommerfield (BPS) as well as non-BPS, is related to the 3-tangle of a 3-qubit state. We relate the 3-qubit states with the string theory states with some number of D-branes. We identify a set of large blackholes with the maximally entangled Greenberger, Horne, Zeilinger (GHZ) class of states and small blackholes with separable, bipartite, and W states. We sort out the relation between 3-qubit states, twistors, octonions, and blackholes. We give a simple expression for the entropy and the area of stretched horizon of small blackholes in terms of a norm and 2-tangles of a 3-qubit system. Finally, we show that the most general expression for the blackhole and black ring entropy in N=8 supergravity/M theory, which is given by the famous quartic Cartan E 7(7) invariant, can be reduced to Cayley's hyperdeterminant describing the 3-tangle of a 3-qubit state

Our Universe contains a great number of extremely compact and massive objects which are generally accepted to be blackholes. Precise observations of orbital motion near candidate blackholes have the potential to determine if they have the spacetime structure that general relativity demands. As a means of formulating measurements to test the blackhole nature of these objects, Collins and Hughes introduced ''bumpy blackholes'': objects that are almost, but not quite, general relativity's blackholes. The spacetimes of these objects have multipoles that deviate slightly from the blackhole solution, reducing to blackholes when the deviation is zero. In this paper, we extend this work in two ways. First, we show how to introduce bumps which are smoother and lead to better behaved orbits than those in the original presentation. Second, we show how to make bumpy Kerr blackholes--objects which reduce to the Kerr solution when the deviation goes to zero. This greatly extends the astrophysical applicability of bumpy blackholes. Using Hamilton-Jacobi techniques, we show how a spacetime's bumps are imprinted on orbital frequencies, and thus can be determined by measurements which coherently track the orbital phase of a small orbiting body. We find that in the weak field, orbits of bumpy blackholes are modified exactly as expected from a Newtonian analysis of a body with a prescribed multipolar structure, reproducing well-known results from the celestial mechanics literature. The impact of bumps on strong-field orbits is many times greater than would be predicted from a Newtonian analysis, suggesting that this framework will allow observations to set robust limits on the extent to which a spacetime's multipoles deviate from the blackhole expectation.

A “clean” blackhole is a blackhole in vacuum such as the Schwarzschild blackhole. However in real physical systems, there are matter fields around a blackhole. Such a blackhole is called a “dirty black hole”. In this paper, the effect of matter fields on the blackhole and the greybody factor is investigated. The results show that matter fields make a blackhole smaller. They can increase the potential energy to a blackhole to obstruct Hawking radiation to propagate. This causes the gre...

This article documents our ongoing search for the elusive "intermediate-mass" blackholes. These would bridge the gap between the approximately ten solar mass "stellar-mass" blackholes that are the end-product of the life of a massive star, and the "supermassive" blackholes with masses of millions to billions of solar masses found at the centers of massive galaxies. The discovery of blackholes with intermediate mass is the key to understanding whether supermassive blackholes can grow from...

We present a construction of a class of near-extremal asymptotically flat blackhole solutions in four (or five) dimensional gauged supergravity with R-symmetry gaugings obtained from Scherk-Schwarz reductions on a circle. The entropy of these blackholes is counted holographically by the well known

Recently Holz and Wheeler considered a very attracting possibility to detect retro-MACHOs, i.e., retro-images of the Sun by a Schwarzschild blackhole. In this paper we discuss glories (mirages) formed near rapidly rotating Kerr blackhole horizons and propose a procedure to measure masses and rotation parameters analyzing these forms of mirages. In some sense that is a manifestation of gravitational lens effect in the strong gravitational field near blackhole horizon and a generalization of the retro-gravitational lens phenomenon. We analyze the case of a Kerr blackhole rotating at arbitrary speed for some selected positions of a distant observer with respect to the equatorial plane of a Kerr blackhole. Some time ago suggested to search shadows at the Galactic Center. In this paper we present the boundaries for shadows. We also propose to use future radio interferometer RADIOASTRON facilities to measure shapes of mirages (glories) and to evaluate the blackhole spin as a function of the position angle of a distant observer. We propose also a procedure to measure a blackhole charge with future space missions. Keywords: blackhole physics, gravitational lenses, microlensing. (authors)

We consider hairy blackhole solutions of Einstein-Yang-Mills-dilaton theory, coupled to a Gauss-Bonnet curvature term, and we study their stability under small, spacetime-dependent perturbations. We demonstrate that stringy corrections do not remove the sphaleronic instabilities of colored blackholes with the number of unstable modes being equal to the number of nodes of the background gauge function. In the gravitational sector and in the limit of an infinitely large horizon, colored blackholes are also found to be unstable. Similar behavior is exhibited by magnetically charged blackholes while the bulk of neutral blackholes are proved to be stable under small, gauge-dependent perturbations. Finally, electrically charged blackholes are found to be characterized only by the existence of a gravitational sector of perturbations. As in the case of neutral blackholes, we demonstrate that for the bulk of electrically charged blackholes no unstable modes arise in this sector. (c) 2000 The American Physical Society

Jan 27, 2016 ... Estimating blackhole masses of blazars is still a big challenge. Because of the contamination of jets, using the previously suggested size–continuum luminosity relation can overestimate the broad line region (BLR) size and blackhole mass for radio-loud AGNs, including blazars. We propose a new relation ...

In classical general relativity the Cauchy horizon within a two-horizon blackhole is unstable via a phenomenon known as mass inflation, in which the mass parameter (and the spacetime curvature) of the blackhole diverges at the Cauchy horizon. Here we study this effect for loop blackholes - quantum gravitationally corrected blackholes from loop quantum gravity - whose construction alleviates the r=0 singularity present in their classical counterparts. We use a simplified model of mass inflation, which makes use of the generalized Dray-'t Hooft relation, to conclude that the Cauchy horizon of loop blackholes indeed results in a curvature singularity similar to that found in classical blackholes. The Dray-'t Hooft relation is of particular utility in the loop blackhole because it does not directly rely upon Einstein's field equations. We elucidate some of the interesting and counterintuitive properties of the loop blackhole, and corroborate our results using an alternate model of mass inflation due to Ori.

Abstract. In the following paper, certain blackhole dynamic potentials have been developed definitively on the lines of classical thermodynam- ics. These potentials have been refined in view of the small differences in the equations of the laws of blackhole dynamics as given by Bekenstein and those of thermodynamics.

Abstract. The work on blackholes immersed in external fields is reviewed in both test-field ap- proximation and within exact solutions. In particular we pay attention to the effect of the expulsion of the flux of external fields across charged and rotating blackholes which are approaching extremal states. Recently this effect has ...

It was recently argued in [1] that blackhole complementarity strains the basic rules of quantum information theory, such as monogamy of entanglement. Motivated by this argument, we develop a practical framework for describing blackhole evaporation via unitary time evolution, based on a holographic

This contribution reviews two topics of current interest in the study of blackhole demographics in active galaxies: Can the stellar velocity dispersions of quasar host galaxies be measured? And can we constrain the blackhole mass function below 10^6 M_⊙?

We discuss the interior of a blackhole in quantum gravity, in which blackholes form and evaporate unitarily. The interior spacetime appears in the sense of complementarity because of special features revealed by the microscopic degrees of freedom when viewed from a semiclassical standpoint. The relation between quantum mechanics and the equivalence principle is subtle, but they are still consistent.

This track is an example of simulated data modelled for the ATLAS detector on the Large Hadron Collider (LHC) at CERN, which will begin taking data in 2008. These tracks would be produced if a miniature blackhole was produced in the proton-proton collision. Such a small blackhole would decay instantly to various particles via a process known as Hawking radiation.

This thesis presents a number of results on partition functions for four-dimensional supersymmetric blackholes. These partition functions are important tools to explain the entropy of blackholes from a microscopic point of view. Such a microscopic explanation was desired after the association of a

Full Text Available Within the framework of blackhole complementarity, a proposal is made for an approximate interior effective field theory description. For generic correlators of local operators on generic blackhole states, it agrees with the exact exterior description in a region of overlapping validity, up to corrections that are too small to be measured by typical infalling observers.

Liberati, Rothman and Sonego have recently showed that objects collapsing into extremal Reissner-Nordstrom blackholes do not behave as thermal objects at any time in their history. In particular, a temperature, and hence thermodynamic entropy, are undefined for them. I demonstrate that the analysis goes through essentially unchanged for Kerr blackholes.

Since the seminal work of Penrose (1969) and Blandford & Znajek (1977), it has been realized that blackhole spin may be an important energy source in astrophysics. The radio-loud/radio-quiet dichotomy in the AGN population is usually attributed to differences in blackhole spin, with correlations

Abstract. The Randall-Sundrum (RS-II) braneworld cosmological model with a frac- tion of the total energy density in primordial blackholes is considered. Due to their 5d geometry, these blackholes undergo modified Hawking evaporation. It is shown that dur- ing the high-energy regime, accretion from the surrounding ...

Abstract. This survey intends to cover recent approaches to blackhole entropy which attempt to go beyond the standard semiclassical perspective. Quantum corrections to the semiclassical Bekenstein–. Hawking area law for blackhole entropy, obtained within the quantum geometry framework, are treated in some detail.

We compute string theoretic blackhole solutions having Lifshitz asymptotics with a general dynamical exponent z > 1. We start by constructing solutions in a flux compactification of six dimensional supergravity, then uplift them to massive type HA supergravity. Alongside the Lifshitz blackholes we

In this paper we derive a class of rotating embedded blackholes. Then we study Hawking's radiation effects on these embedded blackholes. The surface gravity, entropy and angular velocity are given for each of these blackholes.

A program is described which calculates the effects of material falling into the curved space-time surrounding a rotation blackhole. The authors have developed a two-dimensional, general-relativistic hydrodynamics code to simulate fluid flow in the gravitational field of a rotating blackhole. Such calculations represent models that have been proposed for the energy sources of both quasars and jets from radiogalaxies. In each case, the blackhole that powers the quasar or jet would have a mass of about 100 million times the mass of the sun. The blackhole would be located in the center of a galaxy whose total mass is 1000 time greater than the blackhole mass. (SC)

This contribution reviews briefly the various analogies which have been drawn between blackholes and ordinary physical objects. It is shown how, by concentrating on the properties of the surface of a blackhole, it is possible to set up a sequence of tight analogies allowing one to conclude that a blackhole is, qualitatively and quantitatively, similar to a fluid bubble possessing a negative surface tension and endowed with finite values of the electrical conductivity and of the shear and bulk viscosities. These analogies are valid simultaneously at the levels of electromagnetic, mechanical and thermodynamical laws. Explicit applications of this framework are worked out (eddy currents, tidal drag). The thermostatic equilibrium of a blackhole electrically interacting with its surroundings is discussed, as well as the validity of a minimum entropy production principle in blackhole physics. (Auth.)

We find double-extreme blackholes associated with the special geometry of the Calabi-Yau moduli space with the prepotential F=STU. The area formula is STU-moduli independent and has [SL(2,Z)] 3 symmetry in space of charges. The dual version of this theory without a prepotential treats the dilaton S asymmetric vs T,U moduli. We display the dual relation between new (STU) blackholes and stringy (S|TU) blackholes using a particular Sp(8,Z) transformation. The area formula of one theory equals that of the dual theory when expressed in terms of dual charges. We analyze the relation between (STU) blackholes to string triality of blackholes: (S|TU), (T|US), (U|ST) solutions. In the democratic STU-symmetric version we find that all three S, T, and U duality symmetries are nonperturbative and mix electric and magnetic charges. copyright 1996 The American Physical Society

We consider blackholes in Lorentz violating theories of massive gravity. We argue that in these theories blackhole solutions are no longer universal and exhibit a large number of hairs. If they exist, these hairs probe the singularity inside the blackhole providing a window into quantum gravity. The existence of these hairs can be tested by future gravitational wave observatories. We generically expect that the effects we discuss will be larger for the more massive blackholes. In the simplest models the strength of the hairs is controlled by the same parameter that sets the mass of the graviton (tensor modes). Then the upper limit on this mass coming from the inferred gravitational radiation emitted by binary pulsars implies that hairs are likely to be suppressed for almost the entire mass range of the super-massive blackholes in the centers of galaxies

We found double-extreme blackholes associated with the special geometry of the Calabi-Yau moduli space with the prepotential F = STU. The area formula is STU-moduli independent and has [SL(2, Z)]{sup 3} symmetry in space of charges. The dual version of this theory without prepotential treats the dilaton S asymmetric versus T,U-moduli. We display the dual relation between new (STU) blackholes and stringy (S|TU) blackholes using particular Sp(8,Z) transformation. The area formula of one theory equals the area formula of the dual theory when expressed in terms of dual charges. We analyze the relation between (STU) blackholes to string triality of blackholes: (S|TU), (T|US), (U|ST) solutions. In democratic STU-symmetric version we find that all three S and T and U duality symmetries are non-perturbative and mix electric and magnetic charges.

The coalescence of supermassive blackholes--a natural outcome when galaxies merge--should produce gravitational waves and would likely be associated with energetic electromagnetic events. We have studied the coalescence of such binary blackholes within an external magnetic field produced by the expected circumbinary disk surrounding them. Solving the Einstein equations to describe blackholes interacting with surrounding plasma, we present numerical evidence for possible jets driven by these systems. Extending the process described by Blandford and Znajek for a single, spinning blackhole, the picture that emerges suggests that the electromagnetic field extracts energy from the orbiting blackholes, which ultimately merge and settle into the standard Blandford-Znajek scenario. Emissions along these jets could potentially be observable at large distances.

Vacuum bubbles may nucleate during the inflationary epoch and expand, reaching relativistic speeds. After inflation ends, the bubbles are quickly slowed down, transferring their momentum to a shock wave that propagates outwards in the radiation background. The ultimate fate of the bubble depends on its size. Bubbles smaller than certain critical size collapse to ordinary blackholes, while in the supercritical case the bubble interior inflates, forming a baby universe, which is connected to the exterior region by a wormhole. The wormhole then closes up, turning into two blackholes at its two mouths. We use numerical simulations to find the masses of blackholes formed in this scenario, both in subcritical and supercritical regime. The resulting mass spectrum is extremely broad, ranging over many orders of magnitude. For some parameter values, these blackholes can serve as seeds for supermassive blackholes and may account for LIGO observations.

Supermassive blackholes appear to be generic components of galactic nuclei. The formation and growth of blackholes is intimately connected with the evolution of galaxies on a wide range of scales. For instance, mergers between galaxies containing nuclear blackholes would produce supermassive binaries which eventually coalesce via the emission of gravitational radiation. The formation and decay of these binaries is expected to produce a number of observable signatures in the stellar distribution. Blackholes can also affect the large-scale structure of galaxies by perturbing the orbits of stars that pass through the nucleus. Large-scale N-body simulations are beginning to generate testable predictions about these processes which will allow us to draw inferences about the formation history of supermassive blackholes.

What is the nature of the energy spectrum of a blackhole? The algebraic approach to blackhole quantization requires the horizon area eigenvalues to be equally spaced. As stressed long ago by Mukhanov, such eigenvalues must be exponentially degenerate with respect to the area quantum number if one is to understand blackhole entropy as reflecting degeneracy of the observable states. Here we construct the blackhole stationary states by means of a pair of ''creation operators'' subject to a particular simple algebra, a slight generalization of that for a pair of harmonic oscillators. This algebra reproduces the main features of the algebraic approach, in particular the equally spaced area spectrum. We then prove rigorously that the nth area eigenvalue is exactly 2 n -fold degenerate. Thus blackhole entropy qua logarithm of the number of states for a fixed horizon area is indeed proportional to that area

We review the recent noticeable progresses in blackhole physics focusing on the up-coming super-collider, the LHC. We discuss the classical formation of blackholes by particle collision, the greybody factors for higher dimensional rotating blackholes, the deep implications of blackhole physics to the 'energy-distance' relation, the security issues of the LHC associated with blackhole formation and the newly developed Monte-Carlo generators for blackhole events.

Full Text Available There have been lots of debates about the final fate of an evaporating blackhole and the singularity hidden by an event horizon in quantum gravity. However, on general grounds, one may argue that a blackhole stops radiation at the Planck mass (ħc/G1/2∼10−5 g, where the radiated energy is comparable to the blackhole's mass. And also, it has been argued that there would be a wormhole-like structure, known as “spacetime foam”, due to large fluctuations below the Planck length (ħG/c31/2∼10−33 cm. In this paper, as an explicit example, we consider an exact classical solution which represents nicely those two properties in a recently proposed quantum gravity model based on different scaling dimensions between space and time coordinates. The solution, called “Black Wormhole”, consists of two different states, depending on its mass parameter M and an IR parameter ω: For the blackhole state (with ωM2>1/2, a non-traversable wormhole occupies the interior region of the blackhole around the singularity at the origin, whereas for the wormhole state (with ωM2<1/2, the interior wormhole is exposed to an outside observer as the blackhole horizon is disappearing from evaporation. The blackhole state becomes thermodynamically stable as it approaches the merging point where the interior wormhole throat and the blackhole horizon merges, and the Hawking temperature vanishes at the exact merge point (with ωM2=1/2. This solution suggests the “Generalized Cosmic Censorship” by the existence of a wormhole-like structure which protects the naked singularity even after the blackhole evaporation. One could understand the would-be wormhole inside the blackhole horizon as the result of microscopic wormholes created by “negative” energy quanta which have entered the blackhole horizon in Hawking radiation process; the quantum blackhole could be a wormhole factory! It is found that this speculative picture may be consistent with the

ISAAC Finds "Cool" Young Stellar Systems at the Centres of Active Galaxies Summary Supermassive BlackHoles are present at the centres of many galaxies, some weighing hundreds of millions times more than the Sun. These extremely dense objects cannot be observed directly, but violently moving gas clouds and stars in their strong gravitational fields are responsible for the emission of energetic radiation from such "active galaxy nuclei" (AGN) . A heavy BlackHole feeds agressively on its surroundings . When the neighbouring gas and stars finally spiral into the BlackHole, a substantial fraction of the infalling mass is transformed into pure energy. However, it is not yet well understood how, long before this dramatic event takes place, all that material is moved from the outer regions of the galaxy towards the central region. So how is the food for the central BlackHole delivered to the table in the first place? To cast more light on this central question, a team of French and Swiss astronomers [1] has carried out a series of trailblazing observations with the VLT Infrared Spectrometer And Array Camera (ISAAC) on the VLT 8.2-m ANTU telescope at the ESO Paranal Observatory. The ISAAC instrument is particularly well suited to this type of observations. Visible light cannot penetrate the thick clouds of dust and gas in the innermost regions of active galaxies, but by recording the infrared light from the stars close to the BlackHole , their motions can be studied. By charting those motions in the central regions of three active galaxies (NGC 1097, NGC 1808 and NGC 5728), the astronomers were able to confirm the presence of "nuclear bars" in all three. These are dynamical structures that "open a road" for the flow of material towards the innermost region. Moreover, the team was surprised to discover signs of a young stellar population near the centres of these galaxies - stars that have apparently formed quite recently in a central gas disk. Such a system is unstable

Acclaimed science writer John Gribbin recounts dramatic stories that have led scientists to believe blackholes and their more mysterious kin are not only real, but might actually provide a passage to other universes and travel through time.

Could dark matter be made of intermediate-mass blackholes formed in the beginning of the universe? A recent study takes a renewed look at this question.Galactic LurkersThe nature of dark matter has long been questioned, but the recent discovery of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) has renewed interest in the possibility that dark matter could consist of primordial blackholes in the mass range of 101000 solar masses.The relative amounts of the different constituents of the universe. Dark matter makes up roughly 27%. [ESA/Planck]According to this model, the extreme density of matter present during the universes early expansion led to the formation of a large number of intermediate-mass blackholes. These blackholes now hide in the halos of galaxies, constituting the mass that weve measured dynamically but remains unseen.LIGOs first gravitational-wave detection revealed the merger of two blackholes that were both tens of solar masses in size. If primordial blackholes are indeed a major constituent of dark matter, then LIGOs detection is consistent with what we would expect to find: occasional mergers of the intermediate-mass blackholes that formed in the early universe and now lurk in galactic halos.Quasar MicrolensingTheres a catch, however. If there truly were a large number of intermediate-mass primordial blackholes hiding in galactic halos, they wouldnt go completely unnoticed: we would see signs of their presence in the gravitational microlensing of background quasars. Unseen primordial blackholes in a foreground galaxy could cause an image of a background quasar to briefly brighten which would provide us with clear evidence of such blackholes despite our not being able to detect them directly.A depiction of quasar microlensing (click for a closer look!). The microlensing object in the foreground galaxy could be a star (as depicted), a primordial blackhole, or any other compact object. [NASA

We have studied the instability of charged anti-de Sitter blackholes in four- or higher-dimensions under fragmentation. The unstable blackholes under fragmentation can be broken into two blackholes. Instability depends not only on the mass and charge of the blackhole but also on the ratio between the fragmented blackhole and its predecessor. We have found that the near extremal blackholes are unstable, and Schwarzschild-AdS blackholes are stable. These are qualitatively similar to blackholes in four dimensions and higher. The detailed instabilities are numerically investigated.

We consider extremal blackhole solutions to the vacuum Einstein equations in dimensions greater than five. We prove that the near-horizon geometry of any such blackhole must possess an SO(2,1) symmetry in a special case where one has an enhanced rotational symmetry group. We construct examples of vacuum near-horizon geometries using the extremal Myers-Perry blackholes and boosted Myers-Perry strings. The latter lead to near-horizon geometries of black ring topology, which in odd spacetime dimensions have the correct number of rotational symmetries to describe an asymptotically flat black object. We argue that a subset of these correspond to the near-horizon limit of asymptotically flat extremal black rings. Using this identification we provide a conjecture for the exact 'phase diagram' of extremal vacuum black rings with a connected horizon in odd spacetime dimensions greater than five.

Wednesdayevening the Laser Interferometer Gravitational-wave Observatory (LIGO) collaboration quietly mentioned that theyd found gravitational waves from yet another black-hole binary back in June. This casual announcement reveals what is so far the lightest pair of blackholes weve watched merge opening the door for comparisons to the blackholes weve detected by electromagnetic means.A Routine DetectionThe chirp signal of GW170608 detected by LIGO Hanford and LIGO Livingston. [LIGO collaboration 2017]After the fanfare of the previous four black-hole-binary merger announcements over the past year and a half as well as the announcement of the one neutron-star binary merger in August GW170608 marks our entry into the era in which gravitational-wave detections are officially routine.GW170608, a gravitational-wave signal from the merger of two blackholes roughly a billion light-years away, was detected in June of this year. This detection occurred after wed already found gravitational waves from several black-hole binaries with the two LIGO detectors in the U.S., but before the Virgo interferometer came online in Europe and increased the joint ability of the detectors to localize sources.Mass estimates for the two components of GW170608 using different models. [LIGO collaboration 2017]Overall, GW170608 is fairly unremarkable: it was detected by both LIGO Hanford and LIGO Livingston some 7 ms apart, and the signal looks not unlike those of the previous LIGO detections. But because were still in the early days of gravitational-wave astronomy, every discovery is still remarkable in some way! GW170608 stands out as being the lightest pair of blackholes weve yet to see merge, with component masses before the merger estimated at 12 and 7 times the mass of the Sun.Why Size MattersWith the exception of GW151226, the gravitational-wave signal discovered on Boxing Day last year, all of the blackholes that have been discovered by LIGO/Virgo have been quite large: the masses

We study the evolution of cosmological perturbations in a contracting universe. We aim to determine under which conditions density perturbations grow to form large inhomogeneities and collapse into blackholes. Our method consists in solving the cosmological perturbation equations in complete generality for a hydrodynamical fluid. We then describe the evolution of the fluctuations over the different length scales of interest and as a function of the equation of state for the fluid, and we explore two different types of initial conditions: quantum vacuum and thermal fluctuations. We also derive a general requirement for blackhole collapse on sub-Hubble scales, and we use the Press-Schechter formalism to describe the blackhole formation probability. For a fluid with a small sound speed (e.g., dust), we find that both quantum and thermal initial fluctuations grow in a contracting universe, and the largest inhomogeneities that first collapse into blackholes are of Hubble size and the collapse occurs well before reaching the Planck scale. For a radiation-dominated fluid, we find that no blackhole can form before reaching the Planck scale. In the context of matter bounce cosmology, it thus appears that only models in which a radiation-dominated era begins early in the cosmological evolution are robust against the formation of blackholes. Yet, the formation of blackholes might be an interesting feature for other models. We comment on a number of possible alternative early universe scenarios that could take advantage of this feature.

The quantum genesis of Hawking radiation is a long-standing puzzle in blackhole physics. Semi-classically one can argue that the spectrum of radiation emitted by a blackhole look very much sparse unlike what is expected from a thermal object. It was demonstrated through a simple quantum model that a quantum blackhole will retain a discrete profile, at least in the weak energy regime. However, it was suggested that this discreteness might be an artifact of the simplicity of eigen-spectrum of the model considered. Different quantum theories can, in principle, give rise to different complicated spectra and make the radiation from blackhole dense enough in transition lines, to make them look continuous in profile. We show that such a hope from a geometry-quantized blackhole is not realized as long as large enough blackholes are dubbed with a classical mass area relation in any gravity theory ranging from GR, Lanczos–Lovelock to f(R) gravity. We show that the smallest frequency of emission from blackhole in any quantum description, is bounded from below, to be of the order of its inverse mass. That leaves the emission with only two possibilities. It can either be non-thermal, or it can be thermal only with the temperature being much larger than 1/M.

We present the particle creation probability rate around a general blackhole as an outcome of quantum fluctuations. Using the uncertainty principle for these fluctuation, we derive a new ultraviolet frequency cutoff for the radiation spectrum of a dynamical blackhole. Using this frequency cutoff, we define the probability creation rate function for such blackholes. We consider a dynamical Vaidya model and calculate the probability creation rate for this case when its horizon is in a slowly evolving phase. Our results show that one can expect the usual Hawking radiation emission process in the case of a dynamical blackhole when it has a slowly evolving horizon. Moreover, calculating the probability rate for a dynamical blackhole gives a measure of when Hawking radiation can be killed off by an incoming flux of matter or radiation. Our result strictly suggests that we have to revise the Hawking radiation expectation for primordial blackholes that have grown substantially since they were created in the early universe. We also infer that this frequency cut off can be a parameter that shows the primordial blackhole growth at the emission moment. (orig.)

We present the particle creation probability rate around a general blackhole as an outcome of quantum fluctuations. Using the uncertainty principle for these fluctuation, we derive a new ultraviolet frequency cutoff for the radiation spectrum of a dynamical blackhole. Using this frequency cutoff, we define the probability creation rate function for such blackholes. We consider a dynamical Vaidya model and calculate the probability creation rate for this case when its horizon is in a slowly evolving phase. Our results show that one can expect the usual Hawking radiation emission process in the case of a dynamical blackhole when it has a slowly evolving horizon. Moreover, calculating the probability rate for a dynamical blackhole gives a measure of when Hawking radiation can be killed off by an incoming flux of matter or radiation. Our result strictly suggests that we have to revise the Hawking radiation expectation for primordial blackholes that have grown substantially since they were created in the early universe. We also infer that this frequency cut off can be a parameter that shows the primordial blackhole growth at the emission moment. (orig.)

We present the particle creation probability rate around a general blackhole as an outcome of quantum fluctuations. Using the uncertainty principle for these fluctuation, we derive a new ultraviolet frequency cutoff for the radiation spectrum of a dynamical blackhole. Using this frequency cutoff, we define the probability creation rate function for such blackholes. We consider a dynamical Vaidya model and calculate the probability creation rate for this case when its horizon is in a slowly evolving phase. Our results show that one can expect the usual Hawking radiation emission process in the case of a dynamical blackhole when it has a slowly evolving horizon. Moreover, calculating the probability rate for a dynamical blackhole gives a measure of when Hawking radiation can be killed off by an incoming flux of matter or radiation. Our result strictly suggests that we have to revise the Hawking radiation expectation for primordial blackholes that have grown substantially since they were created in the early universe. We also infer that this frequency cut off can be a parameter that shows the primordial blackhole growth at the emission moment.

The quantum genesis of Hawking radiation is a long-standing puzzle in blackhole physics. Semi-classically one can argue that the spectrum of radiation emitted by a blackhole look very much sparse unlike what is expected from a thermal object. It was demonstrated through a simple quantum model that a quantum blackhole will retain a discrete profile, at least in the weak energy regime. However, it was suggested that this discreteness might be an artifact of the simplicity of eigen-spectrum of the model considered. Different quantum theories can, in principle, give rise to different complicated spectra and make the radiation from blackhole dense enough in transition lines, to make them look continuous in profile. We show that such a hope from a geometry-quantized blackhole is not realized as long as large enough blackholes are dubbed with a classical mass area relation in any gravity theory ranging from GR, Lanczos–Lovelock to f(R) gravity. We show that the smallest frequency of emission from blackhole in any quantum description, is bounded from below, to be of the order of its inverse mass. That leaves the emission with only two possibilities. It can either be non-thermal, or it can be thermal only with the temperature being much larger than 1/M.

Mergers of blackhole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates that are too low to be of observational interest. In this Letter, we explore the possibility that blackholes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, blackholes become the most massive objects within a few tens of millions of years; dynamical relaxation then causes them to sink to the cluster core, where they form binaries. These blackhole binaries become more tightly bound by superelastic encounters with other cluster members and are ultimately ejected from the cluster. The majority of escaping blackhole binaries have orbital periods short enough and eccentricities high enough that the emission of gravitational radiation causes them to coalesce within a few billion years. We predict a blackhole merger rate of about 1.6x10-7 yr-1 Mpc-3, implying gravity-wave detection rates substantially greater than the corresponding rates from neutron star mergers. For the first-generation Laser Interferometer Gravitational-Wave Observatory (LIGO-I), we expect about one detection during the first 2 years of operation. For its successor LIGO-II, the rate rises to roughly one detection per day. The uncertainties in these numbers are large. Event rates may drop by about an order of magnitude if the most massive clusters eject their blackhole binaries early in their evolution.

Full Text Available The quantum genesis of Hawking radiation is a long-standing puzzle in blackhole physics. Semi-classically one can argue that the spectrum of radiation emitted by a blackhole look very much sparse unlike what is expected from a thermal object. It was demonstrated through a simple quantum model that a quantum blackhole will retain a discrete profile, at least in the weak energy regime. However, it was suggested that this discreteness might be an artifact of the simplicity of eigen-spectrum of the model considered. Different quantum theories can, in principle, give rise to different complicated spectra and make the radiation from blackhole dense enough in transition lines, to make them look continuous in profile. We show that such a hope from a geometry-quantized blackhole is not realized as long as large enough blackholes are dubbed with a classical mass area relation in any gravity theory ranging from GR, Lanczos–Lovelock to f(R gravity. We show that the smallest frequency of emission from blackhole in any quantum description, is bounded from below, to be of the order of its inverse mass. That leaves the emission with only two possibilities. It can either be non-thermal, or it can be thermal only with the temperature being much larger than 1/M.

We calculate the quantum radiation power of blackholes which are asymptotic to the Einstein-de Sitter universe at spatial and null infinities. We consider two limiting mass accretion scenarios, no accretion and significant accretion. We find that the radiation power strongly depends on not only the asymptotic condition but also the mass accretion scenario. For the no accretion case, we consider the Einstein-Straus solution, where a blackhole of constant mass resides in the dust Friedmann universe. We find negative cosmological correction besides the expected redshift factor. This is given in terms of the cubic root of ratio in size of the blackhole to the cosmological horizon, so that it is currently of order 10 -5 (M/10 6 M o-dot ) 1/3 (t/14Gyr) -1/3 but could have been significant at the formation epoch of primordial blackholes. Due to the cosmological effects, this blackhole has not settled down to an equilibrium state. This cosmological correction may be interpreted in an analogy with the radiation from a moving mirror in a flat spacetime. For the significant accretion case, we consider the Sultana-Dyer solution, where a blackhole tends to increase its mass in proportion to the cosmological scale factor. In this model, we find that the radiation power is apparently the same as the Hawking radiation from the Schwarzschild blackhole of which mass is that of the growing mass at each moment. Hence, the energy loss rate decreases and tends to vanish as time proceeds. Consequently, the energy loss due to evaporation is insignificant compared to huge mass accretion onto the blackhole. Based on this model, we propose a definition of quasi-equilibrium temperature for general conformal stationary blackholes

The recent discovery of large populations of millisec pulsars associated with neutron stars in globular clusters indicates that several hundred stellar blackholes of about 10 solar masses each can form within a typical cluster. While, in clusters of high central density, the rapid dynamical evolution of the black-hole population leads to an ejection of nearly all holes on a short timescale, systems of intermediate density may involve a normal star's capture by one of the surviving holes to form a low-mass X-ray binary. One or more such binaries may be found in the globular clusters surrounding our galaxy.

A simple derivation is given for the leading term (n = 1) in the Schwinger formula for the pair creation by a constant electric field. The same approach is applied then to the charged particle production by a charged blackhole. In this case, as distinct from that of a constant electric field, the probability of the charged particle production depends essentially on the particle energy. The production rate by blackholes is found in the nonrelativistic and ultrarelativistic limits. The range of values for the mass and charge of a blackhole is indicated where the discussed mechanism of radiation dominates the Hawking one.

Recently the possibility of detecting echoes of ringdown gravitational waves from binary blackhole mergers was shown. The presence of echoes is expected if the blackhole is surrounded by a mirror that reflects gravitational waves near the horizon. Here, we present slightly more sophisticated templates motivated by a waveform which is obtained by solving the linear perturbation equation around a Kerr blackhole with a complete reflecting boundary condition in the stationary traveling wave approximation. We estimate that the proposed template can bring about a 10% improvement in the signal-to-noise ratio.

We construct a new class of rotating anti-de Sitter (AdS) blackhole solutions with noncompact event horizons of finite area in any dimension and study their thermodynamics. In four dimensions these blackholes are solutions to gauged supergravity. We find that their entropy exceeds the maximum implied from the conjectured reverse isoperimetric inequality, which states that for a given thermodynamic volume, the blackhole entropy is maximized for Schwarzschild-AdS space. We use this result to suggest more stringent conditions under which this conjecture may hold.

Astrophysical blackhole candidates are thought to be the Kerr blackholes of general relativity, but there is not yet direct observational evidence that the spacetime geometry around these objects is described by the Kerr solution. The study of the properties of the electromagnetic radiation emitted by gas or stars orbiting these objects can potentially test the Kerr blackhole hypothesis. This paper reviews the state of the art of this research field, describing the possible approaches to test the Kerr metric with current and future observational facilities and discussing current constraints.

We present a version of acoustic blackholes by using the principle of the Josephson effect. We find that in the case where two superconductors A and B are separated by an insulating barrier, an acoustic blackhole may be created in the middle region between the two superconductors. We discuss in detail how to describe an acoustic blackhole in the Josephson junction and write the metric in the language of the superconducting electronics. Our final results infer that for big enough tunneling current and thickness of the junction, experimental verification of the Hawking temperature could be possible.

This dissertation presents recent discoveries on partition functions for four-dimensional supersymmetric blackholes. These partition functions are important tools to explain the entropy of blackholes from a microscopic point of view within string theory and M-theory. The results are applied to two central research topics in modern theoretical physics, namely (1) the correspondence between the physics (including gravity) within an Anti-de Sitter space and conformal field theory, and (2) the relation between blackholes and topological strings.

Full Text Available The spectrum of known blackhole solutions to the stationary Einstein equations has increased in an unexpected way during the last decade. In particular, it has turned out that not all blackhole equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum blackhole space-times ceases to exist in self-gravitating non-linear field theories. This text aims to review some of the recent developments and to discuss them in the light of the uniqueness theorem for the Einstein-Maxwell system.

Full Text Available The spectrum of known black-hole solutions to the stationary Einstein equations has been steadily increasing, sometimes in unexpected ways. In particular, it has turned out that not all black-hole-equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro vacuum black-hole spacetimes ceases to exist in self-gravitating non-linear field theories. This text aims to review some developments in the subject and to discuss them in light of the uniqueness theorem for the Einstein-Maxwell system.

We demonstrate that the classical dynamics of blackholes can be reformulated as a dynamical problem of a codimension one membrane moving in flat space. This membrane - roughly the blackhole event horizon - carries a conserved charge current and stress tensor which source radiation. This `membrane paradigm' may be viewed as a simplification of the equations of general relativity at large D, and suggests the possibility of using 1/D as a useful expansion parameter in the analysis of complicated four dimensional solutions of general relativity, for instance the collision between two blackholes.

Full Text Available The elegant ‘no short hair’ theorem states that, if a spherically-symmetric static blackhole has hair, then this hair must extend beyond 3/2 the horizon radius. In the present paper we provide evidence for the failure of this theorem beyond the regime of spherically-symmetric static blackholes. In particular, we show that rotating blackholes can support extremely short-range stationary scalar configurations (linearized scalar ‘clouds’ in their exterior regions. To that end, we solve analytically the Klein–Gordon–Kerr–Newman wave equation for a linearized massive scalar field in the regime of large scalar masses.

Thanks to AdS/CFT, the analogy between blackholes and thermal systems has become a practical tool, shedding light on thermalization, transport, and entanglement dynamics. Continuing in this vein, recent work has shown how chaos in the boundary CFT can be analyzed in terms of high energy scattering right on the horizon of the dual blackhole. The analysis revolves around certain out-of-time-order correlation functions, which are simple diagnostics of the butterfly effect. We will review this work, along with a general bound on these functions that implies blackholes are the most chaotic systems in quantum mechanics. (NB Room Change to Main Auditorium)

The formation of blackholes in quantum cosmology scheme has been discussed by means of calculating the wave function of the universe with a blackhole, which is described by a Schwarzschild-de Sitter metric. We showed that the average radius of the Schwarzschild blackholes formed in the process of the birth of the universe is about lsub(p) 6 H 2 /a 3 , where lsub(p) is the Planck length Λ=3H 2 is the cosmological constant and a is the radius of the universe when it enters into classical era. (author)

The surprising discovery of a supermassive blackhole in a small nearby galaxy has given astronomers a tantalizing look at how blackholes and galaxies may have grown in the early history of the Universe. Finding a blackhole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive blackholes formed before the buildup of galaxies, the astronomers said. The galaxy, called Henize 2-10, 30 million light-years from Earth, has been studied for years, and is forming stars very rapidly. Irregularly shaped and about 3,000 light-years across (compared to 100,000 for our own Milky Way), it resembles what scientists think were some of the first galaxies to form in the early Universe. "This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines, a Ph.D. candidate at the University of Virginia. Supermassive blackholes lie at the cores of all "full-sized" galaxies. In the nearby Universe, there is a direct relationship -- a constant ratio -- between the masses of the blackholes and that of the central "bulges" of the galaxies, leading them to conclude that the blackholes and bulges affected each others' growth. Two years ago, an international team of astronomers found that blackholes in young galaxies in the early Universe were more massive than this ratio would indicate. This, they said, was strong evidence that blackholes developed before their surrounding galaxies. "Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive blackhole. This greatly strengthens the case for the blackholes developing first, before the galaxy's bulge is formed," Reines said. Reines, along with Gregory Sivakoff and Kelsey Johnson of the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and

This work addresses the problem of generically tracking blackhole event horizons in computational simulation of blackhole interactions. Solutions of the hyperbolic eikonal equation, solved on a curved spacetime manifold containing blackhole sources, are employed in development of a robust tracking method capable of continuously monitoring arbitrary changes of topology in the event horizon as well as arbitrary numbers of gravitational sources. The method makes use of continuous families of level set viscosity solutions of the eikonal equation with identification of the blackhole event horizon obtained by the signature feature of discontinuity formation in the eikonal's solution. The method is employed in the analysis of the event horizon for the asymmetric merger in a binary blackhole system. In this first such three dimensional analysis, we establish both qualitative and quantitative evidence for our method and its application to the asymmetric problem. We focus attention on (1) the topology of the throat connecting the holes following merger, (2) the time of merger, and (3) continuing to account for the surface of section areas of the blackhole sources

Even though the existence of the gravitationally collapsed concentrations of matter in space known as ‘black holes’ is accepted at all educational levels in our society, the basis for the blackhole concept is really only the result of approximate calculations done over 40 years ago. The concept of the blackhole is an esoteric subject, and recently the mathematical and physical frailties of the concept have come to light in an interesting round of theoretical shuffling. The recent activity in theorizing about blackholes began about 10 years ago, when Cambridge University mathematican Stephen Hawking calculated that blackholes could become unstable by losing mass and thus ‘evaporate.’ Hawking's results were surprisingly well received, considering the lack of theoretical understanding of the relations between quantum mechanics and relativity. (There is no quantized theory of gravitation, even today.) Nonetheless, his semiclassical calculations implied that the rate of ‘evaporation’ of a blackhole would be slower than the rate of degradation of the universe. In fact, based on these and other calculations, the British regard Hawking as ‘the nearest thing we have to a new Einstein’ [New Scientist, Oct. 9, 1980]. Within the last few months, Frank Tipler, provocative mathematical physicist at the University of Texas, has reexamined Hawking's calculations [Physical Review Letters, 45, 941, 1980], concluding, in simple terms, (1) that because of possible vital difficulties in the assumptions, the very concept of blackholes could be wrong; (2) that Hawkings' evaporation hypothesis is so efficient that a blackhole once created must disappear in less than a second; or (3) that he, Tipler, may be wrong. The latter possibility has been the conclusion of physicist James Bardeen of the University of Washington, who calculated that blackhole masses do evaporate but they do so according to Hawking's predicted rate and that Tipler's findings cause only a second

Astronomers now know that supermassive blackholes reside in nearly every galaxy.Though these blackholes are an observational certainty, nearly every aspect of their evolution -- from their birth, to their fuel source, to their basic dynamics -- is a matter of lively debate. In principle, gas-rich major galaxy mergers can generate the central stockpile of fuel needed for a low mass central blackhole seed to grow quickly into a supermassive one. During a galaxy merger, the blackholes in each galaxy meet and form a supermassive binary blackhole; as the binary orbit shrinks through its final parsec, it becomes the loudest gravitational wave source in the Universe and a powerful agent to sculpt the galactic center. This talk will touch on some current and ongoing work on refining our theories of how supermassive blackhole binaries form, evolve within, and alter their galaxy host.

Since the mid-nineteenth century, both enlisted and fashion-conscious owners of khaki trousers have been plagued by undesired speckle patterns resulting from splash-back while urinating. In recent years, industrial designers and hygiene-driven entrepreneurs have sought to limit this splashing by creating urinal inserts, with the effectiveness of their inventions varying drastically. From this large assortment of inserts, designs consisting of macroscopic pillar arrays seem to be the most effective splash suppressers. Interestingly this design partially mimics the geometry of the water capturing moss Syntrichia caninervis, which exhibits a notable ability to suppress splash and quickly absorb water from impacting rain droplets. With this natural splash suppressor in mind, we search for the ideal urine blackhole by performing experiments of simulated urine streams (water droplet streams) impacting macroscopic pillar arrays with varying parameters including pillar height and spacing, draining and material properties. We propose improved urinal insert designs based on our experimental data in hopes of reducing potential embarrassment inherent in wearing khakis.

It is usually believed that a function φ(t) whose Fourier spectrum is bounded can vary at most as fast as its highest frequency component ωmax. This is, in fact, not the case, as Aharonov, Berry, and others drastically demonstrated with explicit counterexamples, so-called superoscillations. It has been claimed that even the recording of an entire Beethoven symphony can occur as part of a signal with a 1 Hz bandwidth. Bandlimited functions also occur as ultraviolet regularized fields. Their superoscillations have been suggested, for example, to resolve the trans-Planckian frequencies problem of blackhole radiation. Here, we give an exact proof for generic superoscillations. Namely, we show that for every fixed bandwidth there exist functions that pass through any finite number of arbitrarily prespecified points. Further, we show that, in spite of the presence of superoscillations, the behavior of bandlimited functions can be characterized reliably, namely through an uncertainty relation: The standard deviation ΔT of samples φ(tn) taken at the Nyquist rate obeys ΔT>=1/4ωmax. This uncertainty relation generalizes to variable bandwidths. For ultraviolet regularized fields we identify the bandwidth as the in general spatially variable finite local density of degrees of freedom.

We study the thermodynamics of the Schwarzschild-de Sitter blackhole in five dimensions by introducing two temperatures based on the standard and Bousso-Hawking normalizations. We use the first-law of thermodynamics to derive thermodynamic quantities. The two temperatures indicate that the Nariai blackhole is thermodynamically unstable. However, it seems that blackhole thermodynamics favors the standard normalization and does not favor the Bousso-Hawking normalization

We show that the existence of blackholes with classical skyrmion hair invalidates standard proofs that global charges, such as the baryon number, cannot be conserved by a blackhole. By carefully analyzing the standard arguments based on a Gedankenexperiment in which a blackhole is seemingly-unable to return the baryon number that it swallowed, we identify inconsistencies in this reasoning, which does not take into the account neither the existence of skyrmion blackholes nor the baryon/skyrmion correspondence. We then perform a refined Gedankenexperiment by incorporating the new knowledge and show that no contradiction with conservation of baryon number takes place at any stage of blackhole evolution. Our analysis also indicates no conflict between semi-classical blackholes and the existence of baryonic gauge interaction arbitrarily-weaker than gravity. Next, we study classical cross sections of a minimally-coupled massless probe scalar field scattered by a skyrmion blackhole. We investigate how the skyrmion hair manifests itself by comparing this cross section with the analogous cross section caused by a Schwarzschild blackhole which has the same ADM mass as the skyrmion blackhole. Here we find an order-one difference in the positions of the characteristic peaks in the cross sections. The peaks are shifted to smaller scattering angles when the skyrmion hair is present. This comes from the fact that the skyrmion hair changes the near horizon geometry of the blackhole when compared to a Schwarzschild blackhole with same ADM mass. We keep the study of this second aspect general so that the qualitative results which we obtain can also be applied to blackholes with classical hair of different kind.

We consider extended cosmological gravities with Ricci tensor and scalar squared terms in diverse dimensions. These theories admit solutions of Einstein metrics, including the Schwarzschild-Tangherlini AdS blackholes, whose mass and entropy vanish at the critical point. We perform linearized analysis around the blackholes and show that in general the spectrum consists of the usual spin-2 massless and ghost massive modes. We demonstrate that there is no exponentially-growing tachyon mode in the blackholes. At the critical point, the massless spin-2 modes have zero energy whilst the massive spin-2 modes are replaced by the log modes. There always exist certain linear combination of massless and log modes that has negative energy. Thus the stability of the blackholes requires that the log modes to be truncated out by the boundary condition.

Motivated by a recent work of Scardigli, Lambiase and Vagenas (SLV), we derive the GUP parameter, i.e., α0 , when the GUP has a linear and quadratic term in momentum. The value of the GUP parameter is obtained by conjecturing that the GUP-deformed black-hole temperature of a Schwarzschild blackhole and the modified Hawking temperature of a quantum-corrected Schwarzschild blackhole are the same. The leading term in both cases is the standard Hawking temperature and since the corrections are considered as thermal, the modified and deformed expressions of temperature display a slight shift in the Hawking temperature. Finally, by equating the first correction terms, we obtain a value for the GUP parameter. In our analysis, the GUP parameter is not a pure number but depends on the ratio m_\\text{p} /M with m_\\text{p} the Planck mass and M the black-hole mass.

For most blackholes in string theory, the Schwarzschild radius in string units decreases as the string coupling is reduced. We formulate a correspondence principle, which states that (i) when the size of the horizon drops below the size of a string, the typical blackhole state becomes a typical state of strings and D-branes with the same charges, and (ii) the mass does not change abruptly during the transition. This provides a statistical interpretation of blackhole entropy. This approach does not yield the numerical coefficient, but gives the correct dependence on mass and charge in a wide range of cases, including neutral blackholes. copyright 1997 The American Physical Society

A brief overview of the methods commonly used to determine or estimate the blackhole mass in quiescent or active galaxies is presented and it is argued that the use of mass-scaling relations is both a reliable and the preferred method to apply to large samples of distant quasars. The method uses...... that the blackhole masses are very large, of order 1 to 10 billion solar masses, even at the highest redshifts of 4 to 6. The blackholes must build up their mass very fast in the early universe. Yet they do not grow much larger than that: a maximum mass of about 10 billion solar masses is also observed....... Preliminary mass functions of active blackholes are presented for several quasar samples, including the Sloan Digital Sky Survey. Finally, common concerns related to the application of the mass scaling relations, especially for high redshift quasars, are briefly discussed....

Full Text Available A mini-review devoted to some implications of the Hagedorn temperature for blackhole physics. The existence of a limiting temperature is a generic feature of string models. The Hagedorn temperature was introduced first in the context of hadronic physics. Nowadays, the emphasis is shifted to fundamental strings which might be a necessary ingredient to obtain a consistent theory of blackholes. The point is that, in field theory, the local temperature close to the horizon could be arbitrarily high, and this observation is difficult to reconcile with the finiteness of the entropy of blackholes. After preliminary remarks, we review our recent attempt to evaluate the entropy of large blackholes in terms of fundamental strings. We also speculate on implications for dynamics of large-Nc gauge theories arising within holographic models.

Abstract. Basic features of dynamical blackholes in full, non-linear general relativity are summarized in a pedagogical fashion. Qualitative properties of the evolution of various horizons follow directly from the celebrated Raychaudhuri equation.

This talk will focus on simulations of binary blackhole mergers and the gravitational wave signals they produce. Applications to gravitational wave detection with LISA, and electronagnetic counterparts, will be highlighted.

This title reviews in-depth research on accretion on all scales, from galactic binaries to intermediate mass and supermassive blackholes. Possible future directions of accretion are also discussed. The following main themes are covered: a historical perspective; physical models of accretion onto blackholes of all masses; blackhole fundamental parameters; and accretion, jets and outflows. An overview and outlook on the topic is also presented. This volume summarizes the status of the study of astrophysical blackhole research and is aimed at astrophysicists and graduate students working in this field. Originally published in Space Science Reviews, Vol 183/1-4, 2014.

The main results originating from the attempts of trying to incorporate quantum and thermodynamic properties and concepts to the gravitational system blackhole, essentially the Hawking effect and the four laws of thermodynamics are reviewed. (Author) [pt

The near-horizon geometry of a large class of extremal and near-extremal blackholes in string and M-theory contains three-dimensional asymptotically anti-de Sitter space. Motivated by this structure, we are led naturally to a discrete set of complex frequencies defined in terms of the monodromy at the inner and outer horizons of the blackhole. We show that the correspondence principle, whereby the real part of these "nonquasinormal frequencies" is identified with certain fundamental quanta, leads directly to the correct quantum behavior of the near-horizon Virasoro algebra, and thus the blackhole entropy. Remarkably, for the rotating blackhole in five dimensions we also reproduce the fractionization of conformal weights predicted in string theory.

By consideration of a simple example it is demonstrated that a third law of blackhole mechanics cannot be valid unless the energy tensor of accreting matter is bounded and satisfies a positive energy condition outside apparent horizons. (orig.)

Verlinde recently suggested that gravity, inertia, and even spacetime may be emergent properties of an underlying thermodynamic theory. This vision was motivated in part by Jacobson's 1995 surprise result that the Einstein equations of gravity follow from the thermodynamic properties of event horizons. Taking a first tentative step in such a program, we derive the evaporation rate (or radiation spectrum) from blackhole event horizons in a spacetime-free manner. Our result relies on a Hilbert space description of blackhole evaporation, symmetries therein which follow from the inherent high dimensionality of blackholes, global conservation of the no-hair quantities, and the existence of Penrose processes. Our analysis is not wedded to standard general relativity and so should apply to extended gravity theories where we find that the blackhole area must be replaced by some other property in any generalized area theorem.

Jan 27, 2016 ... In this work, we construct a sample of 1585 radio-loud quasars to measure their blackhole masses using broad emission lines. We compare our blackhole masses with the virial blackhole masses measured by Shen et al. (2010).We find that there is a large deviation between them if our blackhole mass is ...

By analyzing the key properties of blackholes from the point of view of quantum information, we derive a model-independent picture of blackhole quantum computing. It has been noticed that this picture exhibits striking similarities with quantum critical condensates, allowing the use of a common language to describe quantum computing in both systems. We analyze such quantum computing by allowing coupling to external modes, under the condition that the external influence must be soft-enough in order not to offset the basic properties of the system. We derive model-independent bounds on some crucial time-scales, such as the times of gate operation, decoherence, maximal entanglement and total scrambling. We show that for blackhole type quantum computers all these time-scales are of the order of the blackhole half-life time. Furthermore, we construct explicitly a set of Hamiltonians that generates a universal set of quantum gates for the blackhole type computer. We find that the gates work at maximal energy efficiency. Furthermore, we establish a fundamental bound on the complexity of quantum circuits encoded on these systems, and characterize the unitary operations that are implementable. It becomes apparent that the computational power is very limited due to the fact that the blackhole life-time is of the same order of the gate operation time. As a consequence, it is impossible to retrieve its information, within the life-time of a blackhole, by externally coupling to the blackhole qubits. However, we show that, in principle, coupling to some of the internal degrees of freedom allows acquiring knowledge about the micro-state. Still, due to the trivial complexity of operations that can be performed, there is no time advantage over the collection of Hawking radiation and subsequent decoding. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

The statistical mechanics of blackholes arbitrarily far from extremality is modeled by a gas of weakly interacting strings. As an effective low-energy description of blackholes the string model provides several highly nontrivial consistency checks and predictions. Speculations on a fundamental origin of the model suggest surprising simplifications in nonperturbative string theory, even in the absence of supersymmetry. copyright 1997 The American Physical Society

Pair creation of electrically charged blackholes and its dual process, pair creation of magnetically charged blackholes, are considered. It is shown that the creation rates are equal provided the boundary conditions for the two processes are dual to one another. This conclusion follows from a careful analysis of boundary terms and boundary conditions for the Maxwell action. copyright 1997 The American Physical Society

Several authors, most notably Heckler, have claimed that the observable Hawking emission from a microscopic blackhole is significantly modified by the formation of a photosphere around the blackhole due to QED or QCD interactions between the emitted particles. In this paper we analyze these claims and identify a number of physical and geometrical effects which invalidate these scenarios. We point out two key problems. First, the interacting particles must be causally connected to interact, and this condition is satisfied by only a small fraction of the emitted particles close to the blackhole. Second, a scattered particle requires a distance ∼E/m e 2 for completing each bremsstrahlung interaction, with the consequence that it is improbable for there to be more than one complete bremsstrahlung interaction per particle near the blackhole. These two effects have not been included in previous analyses. We conclude that the emitted particles do not interact sufficiently to form a QED photosphere. Similar arguments apply in the QCD case and prevent a QCD photosphere (chromosphere) from developing when the blackhole temperature is much greater than Λ QCD , the threshold for QCD particle emission. Additional QCD phenomenological arguments rule out the development of a chromosphere around blackhole temperatures of order Λ QCD . In all cases, the observational signatures of a cosmic or Galactic halo background of primordial blackholes or an individual blackhole remain essentially those of the standard Hawking model, with little change to the detection probability. We also consider the possibility, as proposed by Belyanin et al. and D. Cline et al., that plasma interactions between the emitted particles form a photosphere, and we conclude that this scenario too is not supported.

All presently known relativistic gravitation theories were considered which have a Riemannian background geometry and possess exact static, spherically symmetric solutions which are asymptotically flat. Each theory predicts the existence of trapped surfaces (blackholes). For a general static isotropic metric, MACSYMA was used to compute the Newman-Penrose equations, the blackhole radius, the impact parameter, and capture radius for photon accretion. These results were then applied to several of the better known gravitation theories.

This resource letter is designed to guide students, educators, and researchers through (some of) the literature on blackholes. Both the physics and astrophysics of blackholes are discussed. Breadth has been emphasized over depth, and review articles over primary sources. We include resources ranging from non-technical discussions appropriate for broad audiences to technical reviews of current research. Topics addressed include classification of stationary solutions, perturbations and stabil...

We analyze the stability of a blackhole solution of the Einstein-Yang-Mills equations that was recently found numerically by Bizon, and which provides a counter example for the 'no hair' conjecture for non-abelian blackholes. In the framework of small time-dependent perturbations it is shown that there is at least one exponentially growing radial mode with the correct boundary conditions at the horizon and at infinity. (orig.)

An upcoming study adds to the long history, suggesting blakc holes, now almost taken for granted, never actually comme fully into existence, and that the solution to a decades-old blackhole paradox may be simpler than supposed. (1 page)

Bekenstein and Hawking saved the second law of thermodynamics near a blackhole by assigning to the hole an entropy Ssub(h) proportional to the area of its event horizon. It is tempting to assume that Ssub(h) possesses all the features commonly associated with the physical entropy. Kundt has shown, however, that Ssub(h) violates several reasonable physical expectations. This criticism is reviewed, augmenting it as follows: (a) Ssub(h) is a badly behaved state function requiring knowledge of the hole's future history; and (b) close analogs of event horizons in other space-times do not possess an 'entropy'. These questions are also discussed: (c) Is Ssub(h) suitable for all regions of a black-hole space-time. And (b) should Ssub(h) be attributed to the exterior of a white hole. One can retain Ssub(h) for the interior (respectively, exterior) of a black (respectively, white) hole, but is rejected as contrary to the information-theoretic derivation of horizon entropy given by Berkenstein. The total entropy defined by Kundt (all ordinary entropy on space-section cutting through the hole, no horizon term) and that of Bekenstein-Hawking (ordinary entropy outside horizon plus horizon term) appear to be complementary concepts with separate domains of validity. In the most natural choice, an observer inside a blackhole will use Kundt's entropy, and one remaining outside that of Bekenstein-Hawking. (author)

We review the latest progress in understanding the phase structure of static and neutral Kaluza-Klein blackholes, i.e. static and neutral solutions of pure gravity with an event horizon that asymptote to a d-dimensional Minkowski-space times a circle. We start by reviewing the (mu,n) phase diagram...... and the split-up of the phase structure into solutions with an internal SO(d-1) symmetry and solutions with Kaluza-Klein bubbles. We then discuss the uniform black string, non-uniform black string and localized blackhole phases, and how those three phases are connected, involving issues such as classical...... instability and horizon-topology changing transitions. Finally, we review the bubble-blackhole sequences, their place in the phase structure and interesting aspects such as the continuously infinite non-uniqueness of solutions for a given mass and relative tension....

This review covers the main aspects of blackhole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of blackholes themselves. In this light we discuss how accretion disks might reveal some of the unique signatures of strong gravity: the event horizon, the innermost stable circular orbit, and the ergosphere. We then review, from a first-principles perspective, the physical processes at play in accretion disks. This leads us to the four primary accretion disk models that we review: Polish doughnuts (thick disks), Shakura-Sunyaev (thin) disks, slim disks, and advection-dominated accretion flows (ADAFs). After presenting the models we discuss issues of stability, oscillations, and jets. Following our review of the analytic work, we take a parallel approach in reviewing numerical studies of blackhole accretion disks. We finish with a few select applications that highlight particular astrophysical applications: measurements of blackhole mass and spin, blackhole vs. neutron star accretion disks, blackhole accretion disk spectral states, and quasi-periodic oscillations (QPOs).

We investigate the pair creation of noncommutative blackholes in a background with a positive cosmological constant. As a first step we derive the noncommutative geometry inspired Schwarzschild-de Sitter solution. By varying the mass and the cosmological constant parameters, we find several spacetimes compatible with the new solution: positive-mass spacetimes admit one cosmological horizon and two, one, or no blackhole horizons, while negative-mass spacetimes have just a cosmological horizon. These new blackholes share the properties of the corresponding asymptotically flat solutions, including the nonsingular core and thermodynamic stability in the final phase of the evaporation. As a second step we determine the action which generates the matter sector of gravitational field equations and we construct instantons describing the pair production of blackholes and the other admissible topologies. As a result we find that for current values of the cosmological constant the de Sitter background is quantum mechanically stable according to experience. However, positive-mass noncommutative blackholes and solitons would have plentifully been produced during inflationary times for Planckian values of the cosmological constant. As a special result we find that, in these early epochs of the Universe, Planck size blackholes production would have been largely disfavored. We also find a potential instability for production of negative-mass solitons.

The presence of young massive stars orbiting on eccentric rings within a few tenths of a parsec of the supermassive blackhole in the galactic center is challenging for theories of star formation. The high tidal shear from the blackhole should tear apart the molecular clouds that form stars elsewhere in the Galaxy, and transport of stars to the galactic center also appears unlikely during their lifetimes. We conducted numerical simulations of the infall of a giant molecular cloud that interacts with the blackhole. The transfer of energy during closest approach allows part of the cloud to become bound to the blackhole, forming an eccentric disk that quickly fragments to form stars. Compressional heating due to the blackhole raises the temperature of the gas up to several hundred to several thousand kelvin, ensuring that the fragmentation produces relatively high stellar masses. These stars retain the eccentricity of the disk and, for a sufficiently massive initial cloud, produce an extremely top-heavy distribution of stellar masses. This potentially repetitive process may explain the presence of multiple eccentric rings of young stars in the presence of a supermassive blackhole.

Moffat, J.W. [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada)

2015-04-15

The field equations for scalar-tensor-vector gravity (STVG) or modified gravity (MOG) have a static, spherically symmetric blackhole solution determined by the mass M with two horizons. The strength of the gravitational constant is G = G{sub N} (1 + α) where α is a parameter. A regular singularity-free MOG solution is derived using a nonlinear field dynamics for the repulsive gravitational field component and a reasonable physical energy-momentum tensor. The Kruskal-Szekeres completion of the MOG blackhole solution is obtained. The Kerr-MOG blackhole solution is determined by the mass M, the parameter α and the spin angular momentum J = Ma. The equations of motion and the stability condition of a test particle orbiting the MOG blackhole are derived, and the radius of the blackhole photosphere and the shadows cast by the Schwarzschild-MOG and Kerr-MOG blackholes are calculated. A traversable wormhole solution is constructed with a throat stabilized by the repulsive component of the gravitational field. (orig.)

Inspired by the possibility that the Schwarzschild blackhole may not be the unique spherically symmetric vacuum solution to generalizations of general relativity, we consider blackholes in pure fourth order higher derivative gravity treated as an effective theory. Such solutions may be of interest in addressing the issue of higher derivative hair or during the later stages of blackhole evaporation. Non-Schwarzschild solutions have been studied but we have put earlier results on a firmer footing by finding a systematic asymptotic expansion for the blackholes and matching them with known numerical solutions obtained by integrating out from the near-horizon region. These asymptotic expansions can be cast in the form of trans-series expansions which we conjecture will be a generic feature of non-Schwarzschild higher derivative blackholes. Excitingly we find a new branch of solutions with lower free energy than the Schwarzschild solution, but as found in earlier work, solutions only seem to exist for blackholes with large curvatures, meaning that one should not generically neglect even higher derivative corrections. This suggests that one effectively recovers the nonhair theorems in this context.

We examine what mass spectrum of primordial blackholes should result if the early universe consisted of small density fluctuations superposed on a Friedmann background. It is shown that only a certain type of fluctuation favors the formation of primordial blackholes and that, consequently, their spectrum should always have a particular form. Since both the fluctuations which arise naturally and the fluctuations which are often invoked to explain galaxy formation are of the required type, primordial blackholes could have had an important effect on the evolution of the universe. In particular, although primordial blackholes are unlikely to have a critical density, big one could have been sufficiently numerous to act as condensation nuclei for galaxies. Observational limits on the spectrum of primordial blackholes place strong constraints on the magnitude of density fluctuations in the early universe and support the assumption that the early universe was nearly Friedmann rather than chaotic. Any model in which the early universe has a soft equation of state for a prolonged period is shown to be suspsect, since primordial blackholes probably form too prolifically in such a situation to be consistent with observation

A class of exact rotating blackhole solutions of gravity nonminimally coupled to a self-interacting scalar field in arbitrary dimensions is presented. These spacetimes are asymptotically locally anti-de Sitter manifolds and have a Ricci-flat event horizon hiding a curvature singularity at the origin. The scalar field is real and regular everywhere, and its effective mass, coming from the nonminimal coupling with the scalar curvature, saturates the Breitenlohner-Freedman bound for the corresponding spacetime dimension. The rotating blackhole is obtained by applying an improper coordinate transformation to the static one. Although both spacetimes are locally equivalent, they are globally different, as it is confirmed by the nonvanishing angular momentum of the rotating blackhole. It is found that the mass is bounded from below by the angular momentum, in agreement with the existence of an event horizon. The thermodynamical analysis is carried out in the grand canonical ensemble. The first law is satisfied, and a Smarr formula is exhibited. The thermodynamical local stability of the rotating hairy blackholes is established from their Gibbs free energy. However, the global stability analysis establishes that the vacuum spacetime is always preferred over the hairy blackhole. Thus, the hairy blackhole is likely to decay into the vacuum one for any temperature.

We review recent developments on the thermodynamics of blackholes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. In this approach, the mass of the blackhole is no longer regarded as internal energy, rather it is identified with the chemical enthalpy. This leads to an extended dictionary for blackhole thermodynamic quantities; in particular a notion of thermodynamic volume emerges for a given blackhole spacetime. This volume is conjectured to satisfy the reverse isoperimetric inequality—an inequality imposing a bound on the amount of entropy blackhole can carry for a fixed thermodynamic volume. New thermodynamic phase transitions naturally emerge from these identifications. Namely, we show that blackholes can be understood from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids, reentrant phase transitions, and triple points. We also review the recent attempts at extending the AdS/CFT dictionary in this setting, discuss the connections with horizon thermodynamics, applications to Lifshitz spacetimes, and outline possible future directions in this field. (topical review)

We construct generalizations of the Kerr blackholes by including higher-curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. We show that the domain of existence of these Einstein-Gauss-Bonnet-dilaton (EGBD) blackholes is bounded by the Kerr blackholes, the critical EGBD blackholes, and the singular extremal EGBD solutions. The angular momentum of the EGBD blackholes can exceed the Kerr bound. The EGBD blackholes satisfy a generalized Smarr relation. We also compare their innermost stable circular orbits with those of the Kerr blackholes and show the existence of differences which might be observable in astrophysical systems.

I have derived the Kretschmann scalar for a general blackhole of mass m, angular momentum per unit mass a, and electric charge Q. The Kretschmann scalar gives the amount of curvature of spacetime, as a function of position near (and within) a blackhole. This allows one to display the "appearance" of the blackhole itself, whether the blackhole is merely of stellar mass, or is a supermassive blackhole at the center of an active galaxy. Schwarzschild blackholes, rotating blackholes, elect...

Full Text Available Coalescence of binary supermassive blackholes (SBHs would constitute the strongest sources of gravitational waves to be observed by LISA. While the formation of binary SBHs during galaxy mergers is almost inevitable, coalescence requires that the separation between binary components first drop by a few orders of magnitude, due presumably to interaction of the binary with stars and gas in a galactic nucleus. This article reviews the observational evidence for binary SBHs and discusses how they would evolve. No completely convincing case of a bound, binary SBH has yet been found, although a handful of systems (e.g. interacting galaxies; remnants of galaxy mergers are now believed to contain two SBHs at projected separations of

A longstanding question in stellar evolution is which massive stars produce blackholes (BHs) rather than neutron stars (NSs) upon death. It has been common practice to assume that a given zero-age main sequence (ZAMS) mass star (and perhaps a given metallicity) simply produces either an NS or a BH, but this fails to account for a myriad of other variables that may effect this outcome, such as spin, binarity, or even stochastic differences in the stellar structure near core collapse. We argue that instead a probabilistic description of NS versus BH formation may be better suited to account for the current uncertainties in understanding how massive stars die. We present an initial exploration of the probability that a star will make a BH as a function of its ZAMS mass, P BH(M ZAMS). Although we find that it is difficult to derive a unique P BH(M ZAMS) using current measurements of both the BH mass distribution and the degree of chemical enrichment by massive stars, we demonstrate how P BH(M ZAMS) changes with these various observational and theoretical uncertainties. We anticipate that future studies of Galactic BHs and theoretical studies of core collapse will refine P BH(M ZAMS) and argue that this framework is an important new step toward better understanding BH formation. A probabilistic description of BH formation will be useful as input for future population synthesis studies that are interested in the formation of X-ray binaries, the nature and event rate of gravitational wave sources, and answering questions about chemical enrichment.

A longstanding question in stellar evolution is which massive stars produce blackholes (BHs) rather than neutron stars (NSs) upon death. It has been common practice to assume that a given zero-age main sequence (ZAMS) mass star (and perhaps a given metallicity) simply produces either an NS or a BH, but this fails to account for a myriad of other variables that may effect this outcome, such as spin, binarity, or even stochastic differences in the stellar structure near core collapse. We argue that instead a probabilistic description of NS versus BH formation may be better suited to account for the current uncertainties in understanding how massive stars die. We present an initial exploration of the probability that a star will make a BH as a function of its ZAMS mass, P BH (M ZAMS ). Although we find that it is difficult to derive a unique P BH (M ZAMS ) using current measurements of both the BH mass distribution and the degree of chemical enrichment by massive stars, we demonstrate how P BH (M ZAMS ) changes with these various observational and theoretical uncertainties. We anticipate that future studies of Galactic BHs and theoretical studies of core collapse will refine P BH (M ZAMS ) and argue that this framework is an important new step toward better understanding BH formation. A probabilistic description of BH formation will be useful as input for future population synthesis studies that are interested in the formation of X-ray binaries, the nature and event rate of gravitational wave sources, and answering questions about chemical enrichment

We investigate the thermodynamics of the noncommutative blackhole whose static picture is similar to that of the nonsingular blackhole known as the de Sitter-Schwarzschild blackhole. It turns out that the final remnant of extremal blackhole is a thermodynamically stable object. We describe the evaporation process of this blackhole by using the noncommutativity-corrected Vaidya metric. It is found that there exists a close relationship between thermodynamic approach and evaporation process

In the last decade, the growth of supermassive blackholes (SMBHs) has been intricately linked to galaxy formation and evolution, and is a key ingredient in the assembly of galaxies. Observations of SMBHs with masses of 109 solar at high redshifts (z~7) poses challenges to the theory of seed black

Quantum corrections to the semiclassical Bekenstein–Hawking area law for blackhole entropy, obtained within the quantum geometry framework, are treated in some detail. Their ramiﬁcation for the holographic entropy bound for bounded stationary spacetimes is discussed. Four dimensional supersymmetric extremal black ...

The old suggestive observation that blackholes often resemble lumps of fluid has recently been taken beyond the level of an analogy to a precise duality. We investigate aspects of this duality, and in particular clarify the relation between area minimization of the fluid vs. area maximization of the blackhole horizon, and the connection between surface tension and curvature of the fluid, and surface gravity of the blackhole. We also argue that the Rayleigh-Plateau instability in a fluid tube is the holographic dual of the Gregory-Laflamme instability of a black string. Associated with this fluid instability there is a rich variety of phases of fluid solutions that we study in detail, including in particular the effects of rotation. We compare them against the known results for asymptotically flat blackholes finding remarkable agreement. Furthermore, we use our fluid results to discuss the unknown features of the gravitational system. Finally, we make some observations that suggest that asymptotically flat blackholes may admit a fluid description in the limit of large number of dimensions.

General relativity has passed all solar system experiments and neutron star based tests, such as binary pulsar observations, with flying colors. A more exotic arena for testing general relativity is in systems that contain one or more blackholes. Blackholes are the most compact objects in the Universe, providing probes of the strongest-possible gravitational fields. We are motivated to study strong-field gravity since many theories give large deviations from general relativity only at large field strengths, while recovering the weak-field behavior. In this article, we review how one can probe general relativity and various alternative theories of gravity by using electromagnetic waves from a blackhole with an accretion disk, and gravitational waves from blackhole binaries. We first review model-independent ways of testing gravity with electromagnetic/gravitational waves from a blackhole system. We then focus on selected examples of theories that extend general relativity in rather simple ways. Some important characteristics of general relativity include (but are not limited to) (i) only tensor gravitational degrees of freedom, (ii) the graviton is massless, (iii) no quadratic or higher curvatures in the action, and (iv) the theory is four-dimensional. Altering a characteristic leads to a different extension of general relativity: (i) scalar–tensor theories, (ii) massive gravity theories, (iii) quadratic gravity, and (iv) theories with large extra dimensions. Within each theory, we describe blackhole solutions, their properties, and current and projected constraints on each theory using blackhole based tests of gravity. We close this review by listing some of the open problems in model-independent tests and within each specific theory. (paper)

We construct several classes of worldvolume effective actions for blackholes by integrating out spatial sections of the worldvolume geometry of asymptotically flat black branes. This provides a generalisation of the blackfold approach for higher-dimensional blackholes and yields a map between different effective theories, which we exploit by obtaining new hydrodynamic and elastic transport coefficients via simple integrations. Using Euclidean minimal surfaces in order to decouple the fluid dynamics on different sections of the worldvolume, we obtain local effective theories for ultraspinning Myers-Perry branes and helicoidal black branes, described in terms of a stress-energy tensor, particle currents and non-trivial boost vectors. We then study in detail and present novel compact and non-compact geometries for blackhole horizons in higher-dimensional asymptotically flat space-time. These include doubly-spinning black rings, black helicoids and helicoidal p-branes as well as helicoidal black rings and helicoidal black tori in D≥6.

Full Text Available A new cosmological model called blackhole universe is proposed. According to this model, the universe originated from a hot star-like blackhole with several solar masses, and gradually grew up through a supermassive blackhole with billion solar masses to the present state with hundred billion-trillion solar masses by accreting ambient mate- rials and merging with other blackholes. The entire space is structured with infinite layers hierarchically. The innermost three layers are the universe that we are living, the outside called mother universe, and the inside star-like and supermassive blackholes called child universes. The outermost layer is infinite in radius and limits to zero for both the mass density and absolute temperature. The relationships among all layers or universes can be connected by the universe family tree. Mathematically, the entire space can be represented as a set of all universes. A blackhole universe is a subset of the en- tire space or a subspace. The child universes are null sets or empty spaces. All layers or universes are governed by the same physics - the Einstein general theory of relativity with the Robertson-walker metric of spacetime - and tend to expand outward physically. The evolution of the space structure is iterative. When one universe expands out, a new similar universe grows up from its inside. The entire life of a universe begins from the birth as a hot star-like or supermassive blackhole, passes through the growth and cools down, and expands to the death with infinite large and zero mass density and absolute temperature. The blackhole universe model is consistent with the Mach principle, the observations of the universe, and the Einstein general theory of relativity. Its various aspects can be understood with the well-developed physics without any difficulty. The dark energy is not required for the universe to accelerate its expansion. The inflation is not necessary because the blackhole universe

We develop the representation of infalling observers and bulk fields in the CFT as a way to understand the blackhole interior in AdS. We first discuss properties of CFT states which are dual to blackholes. We then show that in the presence of a Killing horizon bulk fields can be decomposed into pieces we call ingoing and outgoing. The ingoing field admits a simple operator representation in the CFT, even inside a small blackhole at late times, which leads to a simple CFT description of infalling geodesics. This means classical infalling observers will experience the classical geometry in the interior. The outgoing piece of the field is more subtle. In an eternal two-sided geometry it can be represented as an operator on the left CFT. In a stable one-sided geometry it can be described using entanglement via the PR construction. But in an evaporating blackhole trans-horizon entanglement breaks down at the Page time, which means that for old blackholes the PR construction fails and the outgoing field does not see local geometry. This picture of the interior allows the CFT to reconcile unitary Hawking evaporation with the classical experience of infalling observers.

In this paper the question of the emission of fermions in the process of dilaton blackhole evolution and its characteristics for different dilaton coupling constants α are studied. The main quantity of interest, the greybody factors, are calculated both numerically and in analytical approximation. The dependence of the rates of evaporation and behaviour on the dilaton coupling constant is analysed. Having calculated the greybody factors, we are able to address the question of the final fate of the dilaton blackhole. For that we also need to perform dynamical treatment of the solution by considering the backreaction, which will show a crucial effect on the final result. We find a transition line in the (Q/M,α) plane that separates the two regimes for the fate of the blackhole, decay regime and extremal regime. In the decay regime the blackhole completely evaporates, while in the extremal regime the blackhole approaches the extremal limit by radiation and becomes stable. (paper)

The existence of massive blackholes (MBHs) was postulated in the 1960s, when the first quasars were discovered. In the late 1990s their reality was proven beyond doubt in the Milky way and a handful nearby galaxies. Since then, enormous theoretical and observational efforts have been made to understand the astrophysics of MBHs. We have discovered that some of the most massive blackholes known, weighing billions of solar masses, powered luminous quasars within the first billion years of the Universe. The first MBHs must therefore have formed around the time the first stars and galaxies formed. Dynamical evidence also indicates that blackholes with masses of millions to billions of solar masses ordinarily dwell in the centers of today's galaxies. MBHs populate galaxy centers today, and shone as quasars in the past; the quiescent blackholes that we detect now in nearby bulges are the dormant remnants of this fiery past. In this review we report on basic, but critical, questions regarding the cosmological significance of MBHs. What physical mechanisms led to the formation of the first MBHs? How massive were the initial MBH seeds? When and where did they form? How is the growth of blackholes linked to that of their host galaxy? The answers to most of these questions are works in progress, in the spirit of these reports on progress in physics.

Full Text Available Recent results show that important singularities in General Relativity can be naturally described in terms of finite and invariant canonical geometric objects. Consequently, one can write field equations which are equivalent to Einstein's at nonsingular points but, in addition remain well-defined and smooth at singularities. The blackhole singularities appear to be less undesirable than it was thought, especially after we remove the part of the singularity due to the coordinate system. Blackhole singularities are then compatible with global hyperbolicity and do not make the evolution equations break down, when these are expressed in terms of the appropriate variables. The charged blackholes turn out to have smooth potential and electromagnetic fields in the new atlas. Classical charged particles can be modeled, in General Relativity, as charged blackhole solutions. Since blackhole singularities are accompanied by dimensional reduction, this should affect Feynman's path integrals. Therefore, it is expected that singularities induce dimensional reduction effects in Quantum Gravity. These dimensional reduction effects are very similar to those postulated in some approaches to make Quantum Gravity perturbatively renormalizable. This may provide a way to test indirectly the effects of singularities, otherwise inaccessible.

The mass inflation phenomenon implies that blackhole interiors are unstable due to a back-reaction divergence of the perturbed blackhole mass function at the Cauchy horizon. The mass inflation was initially derived by using the generalized Dray–’t Hooft–Redmount (DTR) relation in the linear approximation of the Einstein equations near the perturbed Cauchy horizon of the Reissner–Nordström blackhole. However, this linear approximation for the DTR relation is improper for the highly nonlinear behavior of back-reaction perturbations at the blackhole horizons. An additional weak point in the standard mass inflation calculations is in a fallacious using of the global Cauchy horizon as a place for the maximal growth of the back-reaction perturbations instead of the local inner apparent horizon. It is derived the new spherically symmetric back-reaction solution for two counter-streaming light-like fluxes near the inner apparent horizon of the charged blackhole by taking into account its separation from the Cauchy horizon. In this solution the back-reaction perturbations of the background metric are truly the largest at the inner apparent horizon, but, nevertheless, remain small. The back reaction, additionally, removes the infinite blue-shift singularity at the inner apparent horizon and at the Cauchy horizon. (paper)

We discuss properties of blackholes which are pierced by special configurations of cosmic strings. For static blackholes, we consider radial strings in the limit when the number of strings grows to infinity while the tension of each single string tends to zero. In a properly taken limit, the stress-energy tensor of the string distribution is finite. We call such matter stringy matter. We present a solution of the Einstein equations for an electrically charged static blackhole with the stringy matter, with and without a cosmological constant. This solution is a warped product of two metrics. One of them is a deformed 2-sphere, whose Gaussian curvature is determined by the energy density of the stringy matter. We discuss the embedding of a corresponding distorted sphere into a three-dimensional Euclidean space and formulate consistency conditions. We also found a relation between the square of the Weyl tensor invariant of the four-dimensional spacetime of the stringy blackholes and the energy density of the stringy matter. In the second part of the paper, we discuss test stationary strings in the Kerr geometry and in its Kerr-NUT-(anti-)de Sitter generalizations. Explicit solutions for strings that are regular at the event horizon are obtained. Using these solutions, the stress-energy tensor of the stringy matter in these geometries is calculated. Extraction of the angular momentum from rotating blackholes by such strings is also discussed.

Full text: We have considered the problem which refers to scattering and absorption of perturbations from a blackhole. These perturbations can be scalar, electromagnetic or gravitational waves and satisfy a Schrodinger-type equation, where the potential is specified by the blackhole under consideration. Unfortunately, this problem can not be solved by a standard pseudospectral method, the reason is that does not exist a infinite interval basis set, capable of modelling the ingoing and outgoing waves. By using the rational Chebyshev functions and, adding to it, special functions called 'radiation functions' we are able to compute with high precision the transmission and reflection coefficients. These difficulties emerge, because the rational Chebyshev functions can not correctly represent the asymptotic sine waves present in the work. In order to introduce the various concepts involved in the study of wave scattering by blackholes, we have assumed in this work, the easiest relativistic case, where scalar waves are scattered by a potential generated by a static and spherically symmetric Schwarzschild blackhole. We have adapted and modified the pseudospectral method devised by Boyd, (Computer in Physics, 83 (1990)) which consists in a potential barrier problem in one dimension, the concept of numerical implementation remains the same. The extension of the code for the wave scattering by other blackholes is, also, discussed. (author)

We provide further computations and ideas to the problem of near-Hagedorn string thermodynamics near (uncharged) blackhole horizons, building upon our earlier work http://dx.doi.org/10.1007/JHEP03(2014)086. The relevance of long strings to one-loop blackhole thermodynamics is emphasized. We then provide an argument in favor of the absence of α ′ -corrections for the (quadratic) heterotic thermal scalar action in Rindler space. We also compute the large k limit of the cigar orbifold partition functions (for both bosonic and type II superstrings) which allows a better comparison between the flat cones and the cigar cones. A discussion is made on the general McClain-Roth-O’Brien-Tan theorem and on the fact that different torus embeddings lead to different aspects of string thermodynamics. The blackhole/string correspondence principle for the 2d blackhole is discussed in terms of the thermal scalar. Finally, we present an argument to deal with arbitrary higher genus partition functions, suggesting the breakdown of string perturbation theory (in g s ) to compute thermodynamical quantities in blackhole spacetimes.

Full Text Available We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass blackhole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of matter powers the relativistic jets, responsible for the gamma ray prompt emission. The significant number density of neutrons in the disk and outflowing material will cause subsequent formation of heavier nuclei. We study the process of nucleosynthesis and its possible observational consequences. We also apply our scenario to the recent observation of the gravitational wave signal, detected on 14 September 2015 by the two Advanced LIGO detectors, and related to an inspiral and merger of a binary blackhole system. A gamma ray burst that could possibly be related with the GW150914 event was observed by the Fermi satellite. It had a duration of about 1 s and appeared about 0.4 s after the gravitational-wave signal. We propose that a collapsing massive star and a blackhole in a close binary could lead to the event. The gamma ray burst was powered by a weak neutrino flux produced in the star remnant’s matter. Low spin and kick velocity of the merged blackhole are reproduced in our simulations. Coincident gravitational-wave emission originates from the merger of the collapsed core and the companion blackhole.

The existence of massive blackholes (MBHs) was postulated in the 1960s, when the first quasars were discovered. In the late 1990s their reality was proven beyond doubt in the Milky way and a handful nearby galaxies. Since then, enormous theoretical and observational efforts have been made to understand the astrophysics of MBHs. We have discovered that some of the most massive blackholes known, weighing billions of solar masses, powered luminous quasars within the first billion years of the Universe. The first MBHs must therefore have formed around the time the first stars and galaxies formed. Dynamical evidence also indicates that blackholes with masses of millions to billions of solar masses ordinarily dwell in the centers of today's galaxies. MBHs populate galaxy centers today, and shone as quasars in the past; the quiescent blackholes that we detect now in nearby bulges are the dormant remnants of this fiery past. In this review we report on basic, but critical, questions regarding the cosmological significance of MBHs. What physical mechanisms led to the formation of the first MBHs? How massive were the initial MBH seeds? When and where did they form? How is the growth of blackholes linked to that of their host galaxy? The answers to most of these questions are works in progress, in the spirit of these reports on progress in physics. (review article)

We provide further computations and ideas to the problem of near-Hagedorn string thermodynamics near (uncharged) blackhole horizons, building upon our earlier work http://dx.doi.org/10.1007/JHEP03(2014)086. The relevance of long strings to one-loop blackhole thermodynamics is emphasized. We then provide an argument in favor of the absence of α{sup ′}-corrections for the (quadratic) heterotic thermal scalar action in Rindler space. We also compute the large k limit of the cigar orbifold partition functions (for both bosonic and type II superstrings) which allows a better comparison between the flat cones and the cigar cones. A discussion is made on the general McClain-Roth-O’Brien-Tan theorem and on the fact that different torus embeddings lead to different aspects of string thermodynamics. The blackhole/string correspondence principle for the 2d blackhole is discussed in terms of the thermal scalar. Finally, we present an argument to deal with arbitrary higher genus partition functions, suggesting the breakdown of string perturbation theory (in g{sub s}) to compute thermodynamical quantities in blackhole spacetimes.

Astronomers using ESO's Very Large Telescope have detected, in another galaxy, a stellar-mass blackhole much farther away than any other previously known. With a mass above fifteen times that of the Sun, this is also the second most massive stellar-mass blackhole ever found. It is entwined with a star that will soon become a blackhole itself. The stellar-mass blackholes [1] found in the Milky Way weigh up to ten times the mass of the Sun and are certainly not be taken lightly, but, outside our own galaxy, they may just be minor-league players, since astronomers have found another blackhole with a mass over fifteen times the mass of the Sun. This is one of only three such objects found so far. The newly announced blackhole lies in a spiral galaxy called NGC 300, six million light-years from Earth. "This is the most distant stellar-mass blackhole ever weighed, and it's the first one we've seen outside our own galactic neighbourhood, the Local Group," says Paul Crowther, Professor of Astrophysics at the University of Sheffield and lead author of the paper reporting the study. The blackhole's curious partner is a Wolf-Rayet star, which also has a mass of about twenty times as much as the Sun. Wolf-Rayet stars are near the end of their lives and expel most of their outer layers into their surroundings before exploding as supernovae, with their cores imploding to form blackholes. In 2007, an X-ray instrument aboard NASA's Swift observatory scrutinised the surroundings of the brightest X-ray source in NGC 300 discovered earlier with the European Space Agency's XMM-Newton X-ray observatory. "We recorded periodic, extremely intense X-ray emission, a clue that a blackhole might be lurking in the area," explains team member Stefania Carpano from ESA. Thanks to new observations performed with the FORS2 instrument mounted on ESO's Very Large Telescope, astronomers have confirmed their earlier hunch. The new data show that the blackhole and the Wolf-Rayet star dance

The stability of squashed Kaluza-Klein blackholes is studied. The squashed Kaluza-Klein blackhole looks like a five-dimensional blackhole in the vicinity of horizon and looks like a four-dimensional Minkowski spacetime with a circle at infinity. In this sense, squashed Kaluza-Klein blackholes can be regarded as blackholes in the Kaluza-Klein spacetimes. Using the symmetry of squashed Kaluza-Klein blackholes, SU(2)xU(1)≅U(2), we obtain master equations for a part of the metric perturbations relevant to the stability. The analysis based on the master equations gives strong evidence for the stability of squashed Kaluza-Klein blackholes. Hence, the squashed Kaluza-Klein blackholes deserve to be taken seriously as realistic blackholes in the Kaluza-Klein spacetime.

We investigate thermodynamic curvatures of the Kerr and Reissner-Nordstroem (RN) blackholes in spacetime dimensions higher than four. These blackholes possess thermodynamic geometries similar to those in four-dimensional spacetime. The thermodynamic geometries are the Ruppeiner geometry and the conformally related Weinhold geometry. The Ruppeiner geometry for a d=5 Kerr blackhole is curved and divergent in the extremal limit. For a d≥6 Kerr blackhole there is no extremality but the Ruppeiner curvature diverges where one suspects that the blackhole becomes unstable. The Weinhold geometry of the Kerr blackhole in arbitrary dimension is a flat geometry. For the RN blackhole the Ruppeiner geometry is flat in all spacetime dimensions, whereas its Weinhold geometry is curved. In d≥5 the Kerr blackhole can possess more than one angular momentum. Finally we discuss the Ruppeiner geometry for the Kerr blackhole in d=5 with double angular momenta

New results from NASA's Chandra X-ray Observatory and the Magellan telescopes suggest that a dense stellar remnant has been ripped apart by a blackhole a thousand times as massive as the Sun. If confirmed, this discovery would be a cosmic double play: it would be strong evidence for an intermediate mass blackhole, which has been a hotly debated topic, and would mark the first time such a blackhole has been caught tearing a star apart. This scenario is based on Chandra observations, which revealed an unusually luminous source of X-rays in a dense cluster of old stars, and optical observations that showed a peculiar mix of elements associated with the X-ray emission. Taken together, a case can be made that the X-ray emission is produced by debris from a disrupted white dwarf star that is heated as it falls towards a massive blackhole. The optical emission comes from debris further out that is illuminated by these X-rays. The intensity of the X-ray emission places the source in the "ultraluminous X-ray source" or ULX category, meaning that it is more luminous than any known stellar X-ray source, but less luminous than the bright X-ray sources (active galactic nuclei) associated with supermassive blackholes in the nuclei of galaxies. The nature of ULXs is a mystery, but one suggestion is that some ULXs are blackholes with masses between about a hundred and several thousand times that of the Sun, a range intermediate between stellar-mass blackholes and supermassive blackholes located in the nuclei of galaxies. This ULX is in a globular cluster, a very old and crowded conglomeration of stars. Astronomers have suspected that globular clusters could contain intermediate-mass blackholes, but conclusive evidence for this has been elusive. "Astronomers have made cases for stars being torn apart by supermassive blackholes in the centers of galaxies before, but this is the first good evidence for such an event in a globular cluster," said Jimmy Irwin of the University

The role of vacuum relativization in QCD and nucleus theory is discussed. It is shown that relativistic vacuum must be described by vacuum Einstein equations. BlackHoles have to make their appearance in QCD because of Schwarzschildean solution of these equations. Instanton configurations of any fields do not change vacuum Einstein equations and their solutions, because their energy-momentum tensors are zero. But they make it possible to determine a space-time topology, which cannot be defined by differential Einstein equations. Therefore, BlackHoles number in space-time is possibly connected with instanton configurations of fields and other matter. Instantons do not fall into BlackHoles and are the very matter which surrounds them.

NASA astronomer Kim Weaver has got that sinking feeling. You know, it's that unsettling notion you get when you sift through your X-ray data and, to your surprise, find mid-sized blackholes sinking toward the center of a galaxy, where they merge with others to form a single supermassive blackhole. Could such a thing be true? These would be the largest mergers since America On Line bought Time-Warner, and perhaps even more violent. The process would turn a starburst galaxy inside out, making it more like a quasar host galaxy. Using the Chandra X-Ray Observatory, Weaver saw a hint of this fantastic process in a relatively nearby starburst galaxy named NGC 253 in the constellation Sculptor. She noticed that starburst galaxies - those gems set aglow in a colorful life cycle of hyperactive star birth, death, and renewal - seem to have a higher concentration of mid-mass blackholes compared to other galaxies.

Classic Bondi accretion flow can be generalized to rotating viscous accretion flow. Study of hot accretion flow onto blackholes show that its physical charateristics change from Bondi-like for small gas angular momentum to disk-like for Keperian gas angular momentum. Especially, the mass accretion rate divided by the Bondi accretion rate is proportional to the viscosity parameter alpha and inversely proportional to the gas angular momentum divided by the Keplerian angular momentum at the Bondi radius for gas angular momentum comparable to the Keplerian value. The possible presence of outflow will increase the mass inflow rate at the Bondi radius but decrease the mass accretion rate across the blackhole horizon by many orders of magnitude. This implies that the growth history of supermassive blackholes and their coevolution with host galaxies will be dramatically changed when the accreted gas has angular momentum or develops an outflow.

Full Text Available We consider three dimensional Einstein gravity non-minimally coupled to a real scalar field with a self-interacting scalar potential and present the exact blackhole formation in three dimensions. Firstly we obtain an exact time-dependent spherically symmetric solution describing the gravitational collapse to a scalar blackhole at the infinite time, i.e. in the static limit. The solution can only be asymptotically AdS because of the No–Go theorem in three dimensions which is resulting from the existence of a smooth blackhole horizon. Then we analyze their geometric properties and properties of the time evolution. We also get the exact time-dependent solution in the minimal coupling model after taking a conformal transformation.

We update the constraints on the fraction of the Universe going into primordial blackholes in the mass range 10 9 -10 17 g associated with the effects of their evaporations on big bang nucleosynthesis and the extragalactic photon background. We include for the first time all the effects of quark and gluon emission by blackholes on these constraints and account for the latest observational developments. We then discuss the other constraints in this mass range and show that these are weaker than the nucleosynthesis and photon background limits, apart from a small range 10 13 -10 14 g, where the damping of cosmic microwave background anisotropies dominates. Finally we review the gravitational and astrophysical effects of nonevaporating primordial blackholes, updating constraints over the broader mass range 1-10 50 g.

The entropy and the attractor equations for static extremal blackhole solutions follow from a variational principle based on an entropy function. In the general case such an entropy function can be derived from the reduced action evaluated in a near-horizon geometry. BPS blackholes constitute special solutions of this variational principle, but they can also be derived directly from a different entropy function based on supersymmetry enhancement at the horizon. Both functions are consistent with electric/magnetic duality and for BPS blackholes their corresponding OSV-type integrals give identical results at the semi-classical level. We clarify the relation between the two entropy functions and the corresponding attractor equations for N = 2 supergravity theories with higher-derivative couplings in four space-time dimensions. We discuss how non-holomorphic corrections will modify these entropy functions

We discuss the thermodynamics of higher dimensional blackholes with particular emphasis on a new class of spinning blackholes which, due to the increased number of Casimir invariants, have additional spin degrees of freedom. In suitable limits, analytic solutions in arbitrary dimensions are presented for their temperature, entropy, and specific heat. In 5 + 1 and 9 + 1 dimensions, more general forms for these quantities are given. It is shown that the specific heat for a higher dimensional blackhole is negative definite if it has only one non-zero spin parameter, regardless of the value of this parameter. We also consider equilibrium configurations with both massless particles and massive string modes. 16 refs., 3 figs.

A geometric inequality in general relativity relates quantities that have both a physical interpretation and a geometrical definition. It is well known that the parameters that characterize the Kerr-Newman blackhole satisfy several important geometric inequalities. Remarkably enough, some of these inequalities also hold for dynamical blackholes. This kind of inequalities play an important role in the characterization of the gravitational collapse; they are closely related with the cosmic censorship conjecture. Axially symmetric blackholes are the natural candidates to study these inequalities because the quasi-local angular momentum is well defined for them. We review recent results in this subject and we also describe the main ideas behind the proofs. Finally, a list of relevant open problems is presented. (topical review)

We review the empirical constraints on accretion disk models of stellar-mass blackholes based on recent multiwavelength observational results. In addition to time-averaged emission spectra, the time evolutions of the intensity and spectrum provide critical information about the structure, stability, and dynamics of the disk. Using the basic thermal Keplerian disk paradigm, we consider in particular generalizations of the standard optically thin disk models needed to accommodate the extremely rich variety of dynamical phenomena exhibited by blackhole candidates ranging from flares of electron-positron annihilations and quasiperiodic oscillations in the X-ray intensity to X-ray novae activity. These in turn provide probes of the disk structure and global geometry. The goal is to construct a single unified framework to interpret a large variety of blackhole phenomena. This paper will concentrate on the interface between basic theory and observational data modeling.

The intent of this letter is to point out that the accretion of a ghost condensate by blackholes could be extremely efficient. We analyze steady-state spherically symmetric flows of the ghost fluid in the gravitational field of a Schwarzschild blackhole and calculate the accretion rate. Unlike minimally coupled scalar field or quintessence, the accretion rate is set not by the cosmological energy density of the field, but by the energy scale of the ghost condensate theory. If hydrodynamical flow is established, it could be as high as tenth of a solar mass per second for 10MeV-scale ghost condensate accreting onto a stellar-sized blackhole, which puts serious constraints on the parameters of the ghost condensate model.

Full Text Available Classic Bondi accretion flow can be generalized to rotating viscous accretion flow. Study of hot accretion flow onto blackholes show that its physical charateristics change from Bondi-like for small gas angular momentum to disk-like for Keperian gas angular momentum. Especially, the mass accretion rate divided by the Bondi accretion rate is proportional to the viscosity parameter alpha and inversely proportional to the gas angular momentum divided by the Keplerian angular momentum at the Bondi radius for gas angular momentum comparable to the Keplerian value. The possible presence of outflow will increase the mass inflow rate at the Bondi radius but decrease the mass accretion rate across the blackhole horizon by many orders of magnitude. This implies that the growth history of supermassive blackholes and their coevolution with host galaxies will be dramatically changed when the accreted gas has angular momentum or develops an outflow.

The time evolution of matter fields in blackhole exterior spacetimes is a well-studied subject, spanning several decades of research. However, the behavior of fields in the blackhole interior spacetime has only relatively recently begun receiving some attention from the research community. In this paper, we numerically study the late-time evolution of scalar fields in both Schwarzschild and Kerr spacetimes, including the blackhole interior. We recover the expected late-time power-law "tails" on the exterior (null infinity, timelike infinity, and the horizon). In the interior region, we find an interesting oscillatory behavior that is characterized by the multipole index ℓ of the scalar field. In addition, we also study the extremal Kerr case and find strong indications of an instability developing at the horizon.

The equations of null geodesics in the STU family of rotating blackhole solutions of supergravity theory, which may be considered as deformations of the vacuum Kerr metric, are completely integrable. We propose that they be used as a foil to test, for example, with what precision the gravitational field external to the blackhole at the centre of our galaxy is given by the Kerr metric. By contrast with some metrics proposed in the literature, the STU metrics satisfy by construction the dominant and strong energy conditions. Our considerations may be extended to include the effects of a cosmological term. We show that these metrics permit a straightforward calculation of the properties of blackhole shadows.

One of the goals of the large gravitational wave detectors is eventually to observe radiation from oscillations of neutron stars and blackholes. These objects have characteristic frequencies of what are called 'quasi-normal' mode oscillations, and these frequencies reveal important information about the source. The frequency spectrum of blackholes is very different from that of any stars, so if one or more modes are observed then one can conclusively identify the source as a blackhole. For neutron stars the spectrum is similar to that of main-sequence stars, but observing a single mode is enough to put strong constraints on the nuclear-matter equation of state, something which is still highly uncertain. Current detectors could make these observations only if the source were exceptionally close. But planned upgrades could make the first relativistic asteroseismological observations; in particular the GEO600 detector will be optimised for these observations by 2010.

We discuss the thermodynamics of higher dimensional blackholes with particular emphasis on a new class of spinning blackholes which, due to the increased number of Casimir invariants, have additional spin degrees of freedom. In suitable limits, analytic solutions in arbitrary dimensions are presented for their temperature, entropy, and specific heat. In 5 + 1 and 9 + 1 dimensions, more general forms for these quantities are given. It is shown that the specific heat for a higher dimensional blackhole is negative definite if it has only one non-zero spin parameter, regardless of the value of this parameter. We also consider equilibrium configurations with both massless particles and massive string modes. 16 refs., 3 figs

This book overviews the extensive literature on apparent cosmological and blackhole horizons. In theoretical gravity, dynamical situations such as gravitational collapse, blackhole evaporation, and blackholes interacting with non-trivial environments, as well as the attempts to model gravitational waves occurring in highly dynamical astrophysical processes, require that the concept of event horizon be generalized. Inequivalent notions of horizon abound in the technical literature and are discussed in this manuscript. The book begins with a quick review of basic material in the first one and a half chapters, establishing a unified notation. Chapter 2 reminds the reader of the basic tools used in the analysis of horizons and reviews the various definitions of horizons appearing in the literature. Cosmological horizons are the playground in which one should take baby steps in understanding horizon physics. Chapter 3 analyzes cosmological horizons, their proposed thermodynamics, and several coordinate systems....

The origin of jets emitted from blackholes is not well understood; however, there are two possible energy sources: the accretion disk or the rotating blackhole. Magnetohydrodynamic simulations show a well-defined jet that extracts energy from a blackhole. If plasma near the blackhole is threaded by large-scale magnetic flux, it will rotate with respect to asymptotic infinity, creating large magnetic stresses. These stresses are released as a relativistic jet at the expense of blackhole rotational energy. The physics of the jet initiation in the simulations is described by the theory of blackhole gravitohydromagnetics.

We investigate the accretion of test fluids onto regular blackholes such as Kehagias-Sfetsos blackholes and regular blackholes with Dagum distribution function. We analyze the accretion process when different test fluids are falling onto these regular blackholes. The accreting fluid is being classified through the equation of state according to the features of regular blackholes. The behavior of fluid flow and the existence of sonic points is being checked for these regular blackholes. It is noted that the three-velocity depends on critical points and the equation of state parameter on phase space. (orig.)

We study the charged blackhole of hyperbolic horizon with scalar hair (charged Martinez-Troncoso-Zanelli: CMTZ blackhole) as a model of analytic hairy blackhole for holographic superconductor. For this purpose, we investigate the second order phase transition between CMTZ and hyperbolic Reissner-Nordstroem-AdS (HRNAdS) blackholes. However, this transition unlikely occurs. As an analytic treatment for holographic superconductor, we develop superconductor in the bulk and superfluidity on the boundary using the CMTZ blackhole below the critical temperature. The presence of charge destroys the condensates around the zero temperature, which is in accord with the thermodynamic analysis of the CMTZ blackhole.

Recently q -deformed Einstein equations have been studied for extremal quantum blackholes which have been proposed to obey deformed statistics by Strominger. In this study, we give the solutions of deformed Einstein equations by considering these equations for the charged blackholes. Also we present the implications of the solutions, such as the deformation parameters lead the charged blackholes to have a smaller mass than the classical Reissner- Nordstrom blackholes. The reduction in mass of a classical blackhole can be viewed as a transition from classical to quantum blackhole regime. (paper)

In this work, we discuss the accretion onto static spherically symmetric regular blackholes for specific choices of the equation of state parameter. The underlying regular blackholes are charged regular blackholes using the Fermi-Dirac distribution, logistic distribution, nonlinear electrodynamics, respectively, and Kehagias-Sftesos asymptotically flat regular blackholes. We obtain the critical radius, critical speed, and squared sound speed during the accretion process near the regular blackholes. We also study the behavior of radial velocity, energy density, and the rate of change of the mass for each of the regular blackholes. (orig.)

The event horizon of blackholes and white holes can be achieved in the context of analogue gravity. It was proven for a sonic case that if these two horizons are close to each other their dynamics resemble a laser, a blackhole laser, where the analogue of Hawking radiation is trapped and amplified. Optical analogues are also very successful and a similar system can be achieved there. In this work we develop the theory of optical blackhole lasers and prove that the amplification is also possible. Then, we study the optical system by determining the forward propagation of modes, obtaining an approximation for the phase difference which governs the amplification, and performing numerical simulations of the pulse propagation of our system. - Highlights: • We develop the conditions to obtain the kinematics of the optical blackhole laser. • We prove the amplification of Hawking radiation for the optical case. • We derive the forward propagation of modes and check the result of the backward case. • A model is proposed to calculate the phase difference and the amplification rate. • We perform numerical simulations of a pulse between two solitons forming a cavity.

As a result of significant research over the past 20 years, blackholes are now linked to some of the most spectacular and exciting phenomena in the Universe, ranging in size from those that have the same mass as stars to the super-massive objects that lie at the heart of most galaxies, including our own Milky Way. This book first introduces the properties of simple isolated holes, then adds in complications like rotation, accretion, radiation, and magnetic fields, finally arriving at a basic understanding of how these immense engines work. BlackHole Astrophysics • reviews our current knowledge of cosmic blackholes and how they generate the most powerful observed pheonomena in the Universe; • highlights the latest, most up-to-date theories and discoveries in this very active area of astrophysical research; • demonstrates why we believe that blackholes are responsible for important phenomena such as quasars, microquasars and gammaray bursts; • explains to the reader the nature of the violent and spe...

If gravity becomes strong at the TeV scale, we may have the chance to produce blackholes at particle colliders. In this Letter we revisit some phenomenological signatures of blackhole production in TeV-gravity theories. We show that the bulk-to-brane ratio of blackhole energy loss during the Hawking evaporation phase depends crucially on the blackhole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the blackhole emits mainly on the brane. We also revisit the decay time and the multiplicity of the decay products of blackhole evaporation. We give general formulae for blackhole decay time and multiplicity. We find that the number of particles produced during the evaporation phase may be significantly lower than the average multiplicity which has been used in the past literature

In the AdS/CFT correspondence, states obtained by Hamiltonian evolution of the thermofield doubled state are also dual to an eternal black-hole geometry, which is glued to the boundary with a time shift generated by a large diffeomorphism. We describe gauge-invariant relational observables that probe the blackhole interior in these states and constrain their properties using effective field theory. By adapting recent versions of the information paradox we show that these observables are necessarily described by state-dependent bulk-boundary maps, which we construct explicitly.

We study the blackhole particle production in a regular spacetime metric obtained in a minisuperspace approach to loop quantum gravity. In different previous papers the static solution was obtained and shown to be singularity-free and self-dual. In this paper expanding a previous study of the blackhole dynamics we repeat the Hawking analysis which leads to a thermal flux of particles at the future infinity. The evaporation time is infinite and the unitarity is recovered due to the regularity of the spacetime and to the characteristic behavior of the surface gravity.

The horizon quantum mechanics is an approach that was previously introduced in order to analyze the gravitational radius of spherically symmetric systems and compute the probability that a given quantum state is a blackhole. In this work, we first extend the formalism to general space-times with asymptotic (ADM) mass and angular momentum. We then apply the extended horizon quantum mechanics to a harmonic model of rotating corpuscular blackholes. We find that simple configurations of this model naturally suppress the appearance of the inner horizon and seem to disfavor extremal (macroscopic) geometries. (orig.)

Full Text Available We apply the Bogoliubov transformations in order to connect two different vacuums, one located at past infinity and another located at future infinity around a blackhole inside the scenario of the nonlinear theory of massive gravity. The presence of the extra degrees of freedom changes the behavior of the logarithmic singularity and, as a consequence, the relation between the two Bogoliubov coefficients. This has an effect on the number of particles, or equivalently, on the blackhole temperature perceived by observers defining the time arbitrarily.

Extensions of Einstein gravity with higher-order derivative terms arise in string theory and other effective theories, as well as being of interest in their own right. In this Letter we study static black-hole solutions in the example of Einstein gravity with additional quadratic curvature terms. A Lichnerowicz-type theorem simplifies the analysis by establishing that they must have vanishing Ricci scalar curvature. By numerical methods we then demonstrate the existence of further black-hole solutions over and above the Schwarzschild solution. We discuss some of their thermodynamic properties, and show that they obey the first law of thermodynamics.

We show that, in the AdS/CFT correspondence, states obtained by Hamiltonian evolution of the thermofield doubled state are also dual to an eternal blackhole geometry, which is glued to the boundary with a time shift generated by a large diffeomorphism. We describe gauge invariant relational observables that probe the blackhole interior in these states and constrain their properties using effective field theory. By adapting recent versions of the information paradox we show that these observables are necessarily described by state-dependent bulk-boundary maps, which we construct explicitly.

Different blackhole solutions of the coupled Einstein-Yang-Mills equations have been well known for a long time. They have attracted much attention from mathematicians and physicists since their discovery. In this work, we analyze blackholes associated with the gauge Lorentz group. In particular, we study solutions which identify the gauge connection with the spin connection. This ansatz allows one to find exact solutions to the complete system of equations. By using this procedure, we show the equivalence between the Yang-Mills-Lorentz model in curved space-time and a particular set of extended gravitational theories. (orig.)

We review the latest progress in understanding the phase structure of static and neutral Kaluza-Klein blackholes, i.e. static and neutral solutions of pure gravity with an event horizon and with asymptotics Md × S1, Md being d-dimensional Minkowski space.......We review the latest progress in understanding the phase structure of static and neutral Kaluza-Klein blackholes, i.e. static and neutral solutions of pure gravity with an event horizon and with asymptotics Md × S1, Md being d-dimensional Minkowski space....

Full Text Available We consider Einstein gravities coupled to a cosmological constant and SU(2 Yang–Mills fields in four and five dimensions. We find that the theories admit colored Lifshitz solutions with dynamic exponents z>1. We study the wave equations of the SU(2 scalar triplet in the bulk, and find that the vacuum color modifies the scaling dimensions of the dual operators. We also introduce a Maxwell field and construct exact solutions of electrically-charged blackholes that approach the D=4, z=3 and D=5, z=4 colored Lifshitz spacetimes. We derive the thermodynamical first law for general colored and charged Lifshitz blackholes.

We study the correction to the scale invariant power spectrum of a scalar field on de Sitter space from small blackholes that formed during a pre-inflationary matter dominated era. The formation probability of such blackholes is estimated from primordial Gaussian density fluctuations. We determine the correction to the spectrum of scalar cosmological perturbations from the Keldysh propagator of a massless scalar field on Schwarzschild-de Sitter space. Our results suggest that the effect is strong enough to be tested — and possibly even ruled out — by observations.

AdS blackholes with hyperbolic horizons provide strong-coupling descriptions of thermal CFT states on hyperboloids. The low-temperature limit of these systems is peculiar. In this note we show that, in addition to a large ground state degeneracy, these states also have an anomalously large holographic complexity, scaling logarithmically with the temperature. We speculate on whether this fact generalizes to other systems whose extreme infrared regime is formally controlled by Conformal Quantum Mechanics, such as various instances of near-extremal charged blackholes.

Full Text Available A brief history of the idea of blackhole, since the formulation of the Theory of General Relativity to recent observations, is presented. During the twentieth century the idea evolved from mere theoretical speculation to play a central role to explain the most luminous objects in the universe: the quasars. It is believed, today, that the blackholes and galaxies have had close co-evolution and both could not exist without the other, at least not in the way that we observe them.

Using effective field theory techniques, we compute quantum corrections to spherically symmetric solutions of Einstein's gravity and focus in particular on the Schwarzschild blackhole. Quantum modifications are covariantly encoded in a non-local effective action. We work to quadratic order in curvatures simultaneously taking local and non-local corrections into account. Looking for solutions perturbatively close to that of classical general relativity, we find that an eternal Schwarzschild blackhole remains a solution and receives no quantum corrections up to this order in the curvature expansion. In contrast, the field of a massive star receives corrections which are fully determined by the effective field theory. (orig.)

A red hole is "just like a blackhole" except it lacks an event horizon and a singularity. As a result, a red hole emits much more energy than a blackhole during a collapse or accretion event. We consider how a red hole solution can solve the "energy crisis" and power extremely energetic gamma ray bursts and hypernovae.

Thanks to two orbiting X-ray observatories, astronomers have the first strong evidence of a supermassive blackhole ripping apart a star and consuming a portion of it. The event, captured by NASA's Chandra and ESA's XMM-Newton X-ray Observatories, had long been predicted by theory, but never confirmed. Astronomers believe a doomed star came too close to a giant blackhole after being thrown off course by a close encounter with another star. As it neared the enormous gravity of the blackhole, the star was stretched by tidal forces until it was torn apart. This discovery provides crucial information about how these blackholes grow and affect surrounding stars and gas. "Stars can survive being stretched a small amount, as they are in binary star systems, but this star was stretched beyond its breaking point," said Stefanie Komossa of the Max Planck Institute for Extraterrestrial Physics (MPE) in Germany, leader of the international team of researchers. "This unlucky star just wandered into the wrong neighborhood." While other observations have hinted stars are destroyed by blackholes (events known as "stellar tidal disruptions"), these new results are the first strong evidence. Evidence already exists for supermassive blackholes in many galaxies, but looking for tidal disruptions represents a completely independent way to search for blackholes. Observations like these are urgently needed to determine how quickly blackholes can grow by swallowing neighboring stars. Animation of Star Ripped Apart by Giant BlackHole Star Ripped Apart by Giant BlackHole Observations with Chandra and XMM-Newton, combined with earlier images from the German Roentgen satellite, detected a powerful X-ray outburst from the center of the galaxy RX J1242-11. This outburst, one of the most extreme ever detected in a galaxy, was caused by gas from the destroyed star that was heated to millions of degrees Celsius before being swallowed by the blackhole. The energy liberated in the process

When a normally dormant supermassive blackhole burps out a brief flare, its assumed that a star was torn apart and fell into the blackhole. But a new study suggests that some of these flares might have a slightly different cause.Not a Disruption?Artists impression of a tidal disruption event, in which a star has been pulled apart and its gas feeds the supermassive blackhole. [NASA/JPL-Caltech]When a star swings a little too close by a supermassive blackhole, the blackholes gravity can pull the star apart, completely disrupting it. The resulting gas can then accrete onto the blackhole, feeding it and causing it to flare. The predicted frequency of these tidal disruption events and their expected light curves dont perfectly match all our observations of flaring blackholes, however.This discrepancy has led two scientists from the Columbia Astrophysics Laboratory, Brian Metzger and Nicholas Stone, to wonder if we can explain flares from supermassive blackholes in another way. Could a differentevent masquerade as a tidal disruption?Evolution of a stars semimajor axis (top panel) and radius (bottom panel) as a function of time since Roche-lobe overflow began onto a million-solar-mass blackhole. Curves show stars of different masses. [Metzger Stone 2017]Inspirals and OutspiralsIn the dense nuclear star cluster surrounding a supermassive blackhole, various interactions can send stars on new paths that take them close to the blackhole. In many of these interactions, the stars will end up on plunging orbits, often resulting in tidal disruption. But sometimes stars can approach the blackhole on tightly bound orbits with lower eccentricities.A main-sequence star on such a path, in what is known as an extreme mass ratio inspiral (EMRI), slowly approaches the blackhole over a period of millions of years, eventually overflowing its Roche lobe and losing mass. Theradius of the star inflates, driving more mass loss and halting the stars inward progress. The star then

Rapidly rotating Myers-Perry blackholes in d≥6 dimensions were conjectured to be unstable by Emparan and Myers. In a previous publication, we found numerically the onset of the axisymmetric ultraspinning instability in the singly spinning Myers-Perry blackhole in d=7, 8, 9. This threshold also signals a bifurcation to new branches of axisymmetric solutions with pinched horizons that are conjectured to connect to the black ring, black Saturn and other families in the phase diagram of stationary solutions. We firmly establish that this instability is also present in d=6 and in d=10, 11. The boundary conditions of the perturbations are discussed in detail for the first time, and we prove that they preserve the angular velocity and temperature of the original Myers-Perry blackhole. This property is fundamental to establishing a thermodynamic necessary condition for the existence of this instability in general rotating backgrounds. We also prove a previous claim that the ultraspinning modes cannot be pure gauge modes. Finally we find new ultraspinning Gregory-Laflamme instabilities of rotating black strings and branes that appear exactly at the critical rotation predicted by the aforementioned thermodynamic criterium. The latter is a refinement of the Gubser-Mitra conjecture.

This past December, researchers all over the world watched an outburst from the enormous blackhole in OJ 287 an outburst that had been predicted years ago using the general theory of relativity.Outbursts from Black-Hole OrbitsOJ 287 is one of the largest supermassive blackholes known, weighing in at 18 billion solar masses. Located about 3.5 billion light-years away, this monster quasar is bright enough that it was first observed as early as the 1890s. What makes OJ 287 especially interesting, however, is that its light curve exhibits prominent outbursts roughly every 12 years.Diagram illustrating the orbit of the secondary blackhole (shown in blue) in OJ 287 from 2000 to 2023. We see outbursts (the yellow bubbles) every time the secondary blackhole crosses the accretion disk (shown in red, ina side view) surrounding the primary (the black circle). [Valtonen et al. 2016]What causes the outbursts? Astronomers think that there is a second supermassive blackhole, ~100 times smaller, inspiraling as it orbits the central monster and set to merge within the next 10,000 years. In this model, the primary blackhole of OJ 287 is surrounded by a hot accretion disk. As the secondary blackhole orbits the primary, it regularly punches through this accretion disk, heating the material and causing the release of expanding bubbles of hot gas pulled from the disk. This gas then radiates thermally, causing the outbursts we see.Attempts to model this scenario using Newtonian orbits all fail; the timing of the secondary blackholes crossings through the accretion disk (as measured by when we see the outbursts) can only be explained by a model incorporating general-relativistic effects on the orbit. Careful observations and precise timing of these outbursts therefore provide an excellent test of general relativity.Watching a Predicted CrossingThe model of OJ 287 predicted another disk crossing in December 2015, so professional and amateur astronomers around the world readied more

Three-body interactions are expected to be common in globular clusters and in galactic cores hosting supermassive blackholes. We consider an equal-mass binary blackhole system in the presence of a third blackhole. Using numerically generated binary blackhole initial data sets, and first and second-order post-Newtonian (1PN and 2PN) techniques, we find that the presence of the third blackhole has non-negligible relativistic effects on the location of the binary's innermost stable circular orbit (ISCO), and that these effects arise at 2PN order. For a stellar-mass blackhole binary in orbit about a supermassive blackhole, the massive blackhole has stabilizing effects on the orbiting binary, leading to an increase in merger time and a decrease of the terminal orbital frequency, and an amplification of the gravitational radiation emitted from the binary system by up to 6%

In recent years, the thermodynamic properties of blackholes are topics of interests. We investigate the thermodynamic properties like surface gravity and Hawking temperature on event horizon of regular blackholes viz. Hayward Class and asymptotically AdS (Anti-de Sitter) blackholes. We also analyze the thermodynamic volume and naive geometric volume of asymptotically AdS blackholes and show that the entropy of these blackholes is simply the ratio of the naive geometric volume to thermodynamic volume. We plot the different graphs and interpret them physically. We derive the `cosmic-Censorship-Inequality' for both type of blackholes. Moreover, we calculate the thermal heat capacity of aforesaid blackholes and study their stabilities in different regimes. Finally, we compute the logarithmic correction to the entropy for both the blackholes considering the quantum fluctuations around the thermal equilibrium and study the corresponding thermodynamics.

We study the conditions for 2-dimensional dilaton gravity models to have dynamical formation of blackholes and construct all such models. Furthermore we present a parametric representation of the general solutions of the blackholes.

We investigate the fragmentation instability of hairy blackholes in the theory with a Gauss-Bonnet (GB) term in asymptotically flat spacetime. Our approach is through the non-perturbative fragmentation instability. By this approach, we investigate whether the initial blackhole can be broken into two blackholes by comparing the entropy of the initial blackhole with the sum of those of two fragmented blackholes. The relation between the blackhole instability and the GB coupling with dilaton hair are presented. We describe the phase diagrams with respect to the mass of the blackhole solutions and coupling constants. We find that a perturbatively stable blackhole can be unstable under fragmentation. (orig.)

We study the thermodynamic phase transition in the rainbow Schwarzschild blackhole where the metric depends on the energy of the test particle. Identifying the blackhole temperature with the energy from the modified dispersion relation, we obtain the modified entropy and thermodynamic energy along with the modified local temperature in the cavity to provide well defined blackhole states. It is found that apart from the conventional critical temperature related to Hawking-Page phase transition there appears an additional critical temperature which is of relevance to the existence of a locally stable tiny blackhole; however, the off-shell free energy tells us that this blackhole should eventually tunnel into the stable large blackhole. Finally, we discuss the reason why the temperature near the horizon is finite in the rainbow blackhole by employing the running gravitational coupling constant, whereas it is divergent near the horizon in the ordinary Schwarzschild blackhole

Blackholes are considered as objects that can reveal quantum aspects of spacetime. Loop Quantum Gravity (LQG) is a theory that propose a way to model the quantum spacetime behavior revealed by a blackhole. One recent prediction of this theory is the existence of sub-Planckian blackholes, which have the interesting property of self-duality. This property removes the blackhole singularity and replaces it with another asymptotically flat region. In this work, we obtain the thermodynamical properties of this kind of blackholes, called self-dual blackholes, using the Hamilton–Jacobi version of the tunneling formalism. Moreover, using the tools of the tunneling approach, we investigate the emission spectrum of self-dual blackholes, and investigate if some information about the blackhole initial state can be recovered during the evaporation process. Back-reaction effects are included.

Full Text Available The mathematical proof of existence of BlackHole is based on the assumption of mass being independent of speed. Considering the effect of special relativity of the dependence of mass with speed there is no Blackhole.

Four probable detections of gravitational waves have so far been reported, each associated with the merger of two blackholes. Analysis of the signals allows formation theories of such black-hole systems to be tested. See Letter p.426

We investigate the topology of Schwarzschild's blackhole through the immersion of this space-time in spaces of higher dimension. Through the immersions of Kasner and Fronsdal we calculate the extension of the Schwarzschild's blackhole.

We consider the two classes cosh and sinh of normal and phantom blackholes of Einstein-Maxwell-dilaton theory. The thermodynamics of these holes is characterized by heat capacities that may have both signs depending on the parameters of the theory. Leaving aside the normal Reissner-Nordström blackhole, it is shown that only some phantom blackholes of both classes exhibit critical phenomena. The two classes share a nonextremality, but special, critical point where the transition is continuous and the heat capacity, at constant charge, changes sign with an infinite discontinuity. This point yields a classification scheme for critical points. It is concluded that the two unstable and stable phases coexist on one side of the criticality state and disappear on the other side, that is, there is no configuration where only one phase exists. The sinh class has an extremality critical point where the entropy diverges. The transition from extremality to nonextremality with the charge held constant is accompanied by a loss of mass and an increase in the temperature. A special case of this transition is when the hole is isolated (microcanonical ensemble), it will evolve by emission of energy, which results in a decrease of its mass, to the final state of minimum mass and vanishing heat capacity. The Ehrenfest scheme of classification is inaccurate in this case but the generalized one due to Hilfer leads to conclude that the transition is of order less than unity. Fluctuations near criticality are also investigated.

Jan 27, 2016 ... Abstract. Using a new tortoise coordinate transformation, the Hawking radiation of the acoustic blackhole was discussed by studying the Klein–Gordon equation of scalar particles in the curve space-time. It was found that the Hawking temperature is connected with time and position on the event horizon.

Hawking particles emitted by a blackhole are usually found to have thermal spectra, if not exactly, then by a very good approximation. Here, we argue differently. It was discovered that spherical partial waves of in-going and out-going matter can be described by unitary evolution operators

We construct and study stationary, asymptotically flat multicenter solutions describing regular blackholes with non-Abelian hair (colored magnetic-monopole and dyon fields) in two models of N=2 , d = 4 Super-Einstein-Yang-Mills theories: the quadratic model \\overline{CP}^3 and the cubic model ST[2, 6], which can be embedded in 10-dimensional Heterotic Supergravity. These solutions are based on the multicenter dyon recently discovered by one of us, which solves the SU(2) Bogomol'nyi and dyon equations on E^3 . In contrast to the well-known Abelian multicenter solutions, the relative positions of the non-Abelian black-hole centers are unconstrained. We study necessary conditions on the parameters of the solutions that ensure the regularity of the metric. In the case of the \\overline{CP}^3 model we show that it is enough to require the positivity of the "masses" of the individual blackholes, the finiteness of each of their entropies and their superadditivity. In the case of the ST[2, 6] model we have not been able to show that analogous conditions are sufficient, but we give an explicit example of a regular solution describing thousands of non-Abelian dyonic blackholes in equilibrium at arbitrary relative positions. We also construct non-Abelian solutions that interpolate smoothly between just two aDS2×S2 vacua with different radii ( dumbbell solutions).

The European Center for Nuclear Research or CERN's Large Hadron Collider (LHC) has caught our attention partly due to the film "Angels and Demons." In the movie, an antimatter bomb attack on the Vatican is foiled by the protagonist. Perhaps just as controversial is the formation of mini blackholes (BHs). Recently, the American Physical Society…

A consequence of the evaporation of primordial blackholes in the early universe may be the generation of mirror matter. This would have implications with regard to dark matter, and the number of light particle species in equilibrium at the time of big bang nucleosynthesis. The possibilities for the production of mirror matter by this mechanism are explored.

The first Advanced LIGO observing run detected two blackhole merger events with confidence and likely a third. Many groups organized to followup the events in the optical even though the strong theoretical prior that no optical emission should be seen. We carry through the logic of this by asking about the experimental upper limits to the optical light from Advanced LIGO blackhole mergere events. We inventory the published optical searches for transient events associated with the blackhole mergers. We describe the factors that go into a formal limit on the visibility of an event (sky area coverage, the coverage factor of the camera, the fraction of sky not covered by intervening objects), and list what is known from the literature of the followup teams quantitative assessment of each factor. Where possible we calculate the total probability from each group that the source was imaged. The calculation of confidence level is reviewed for the case of no background. We find that an experimental 95% upper limit on the magnitude of a blackhole requires the sum of the total probabilities over all events to be more than 3. In the first Advanced LIGO observing run we were far from reaching that threshold.

The formation of supermassive blackholes (SMBH) is intimately related to galaxy formation, although precisely how remains a mystery. I speculate that formation of, and feedback from, SMBH may alleviate problems that have arisen in our understanding of the cores of dark halos of galaxies.

An exact expression for the quasinormal modes of scalar perturbation on a massless topological blackhole in four and higher dimensions is presented. The massive scalar field is nonminimally coupled to the curvature, and the horizon geometry is assumed to have a negative constant curvature

This is a review of results on blackhole physics in the context of loop quantum gravity. The key feature underlying these results is the discreteness of geometric quantities at the Planck scale predicted by this approach to quantum gravity. Quantum discreteness follows directly from the canonical quantization prescription when applied to the action of general relativity that is suitable for the coupling of gravity with gauge fields, and especially with fermions. Planckian discreteness and causal considerations provide the basic structure for the understanding of the thermal properties of blackholes close to equilibrium. Discreteness also provides a fresh new look at more (at the moment) speculative issues, such as those concerning the fate of information in blackhole evaporation. The hypothesis of discreteness leads, also, to interesting phenomenology with possible observational consequences. The theory of loop quantum gravity is a developing program; this review reports its achievements and open questions in a pedagogical manner, with an emphasis on quantum aspects of blackhole physics.

This is a summary of the papers presented in session W2 on a fairly wide-ranging variety of topics in the area of blackhole physics and quantum aspects of gravity, including quantum ﬁeld and string theory in curved spacetimes. In addition, experts in a couple of topical subjects were invited to present short surveys on the ...

Analysis of a massive shell collapsing on a solid sphere shows that blackhole complementarity (BHC) violates causality in its effort to save information conservation. In particular, this note describes a hypothetical contraption based on BHC that would allow the transfer of information from the future to the present.

In the AdS/CFT correspondence, states obtained by Hamiltonian evolution of the thermofield doubled state are also dual to an eternal black-hole geometry, which is glued to the boundary with a time shift generated by a large diffeomorphism. We describe gauge-invariant relational observables that

In this paper, we study the CFT duals for extreme blackholes in the stretched horizon formalism. We consider the extremal RN, Kerr-Newman-AdS-dS, as well as the higher dimensional Kerr-AdS-dS blackholes. In all these cases, we reproduce the well-established CFT duals. Actually we show that for stationary extreme blackholes, the stretched horizon formalism always gives rise to the same dual CFT pictures as the ones suggested by ASG of corresponding near horizon geometries. Furthermore, we propose new CFT duals for 4D Kerr-Newman-AdS-dS and higher dimensional Kerr-AdS-dS blackholes. We find that every dual CFT is defined with respect to a rotation in certain angular direction, along which the translation defines a U(1) Killing symmetry. In the presence of two sets of U(1) symmetry, the novel CFT duals are generated by the modular group SL(2,Z), and for n sets of U(1) symmetry there are general CFT duals generated by T-duality group SL(n,Z).

In the present work I focus attention on the construction of suitably general initial data, with particular attention to some new results that enable consideration of blackholes that can possess spin (and electric charge) as well as orbital motion. (orig.)

The next generation of particle accelerators, like the LHC, may be able to produce minature blackholes. At the same time the experiments will explore the theory that the universe consists of hidden dimensions, outside the three we are familiar with (1 page).

A massive vector field inside the event horizon created by the static sources located outside the blackhole is investigated. It is shown that the back reaction of such a field on the metric near r = 0 cannot be neglected. The possibility of the space-time structure changing near r = 0 due to the external massive field is discussed

We study the quantum modifications of classical, spherically symmetric Schwarzschild (anti-) de Sitter blackholes within quantum Einstein gravity. The quantum effects are incorporated through the running coupling constants Gk and Λk, computed within the exact renormalization group approach, and a common scale-setting procedure. We find that, in contrast to common intuition, it is actually the cosmological constant that determines the short-distance structure of the RG-improved blackhole: in the asymptotic UV the structure of the quantum solutions is universal and given by the classical Schwarzschild-de Sitter solution, entailing a self-similarity between the classical and quantum regime. As a consequence asymptotically safe blackholes evaporate completely and no Planck-size remnants are formed. Moreover, the thermodynamic entropy of the critical Nariai blackhole is shown to agree with the microstate count based on the effective average action, suggesting that the entropy originates from quantum fluctuations around the mean-field geometry.

In this paper the low temperature zero-frequency transport in a 2 + 1-dimensional theory dual to a dyonic blackhole is discussed. It is shown that transport exhibits topological features: the transverse electric and heat conductivities satisfy the Wiedemann-Franz law of free electrons; the direct heat conductivity is measured in units of the central charge of CFT2+1, while the direct electric conductivity vanishes; the thermoelectric conductivity is non-zero at vanishing temperature, while the O (T) behavior, controlled by the Mott relation, is subleading. Provided that the entropy of the blackhole, and the dual system, is non-vanishing at T = 0, the observations indicate that the dyonic blackhole describes a ħ → 0 limit of a highly degenerate topological state, in which the blackhole charge measures the density of excited non-abelian quasiparticles. The holographic description gives further evidence that non-abelian nature of quasiparticles can be determined by the low temperature behavior of the thermoelectric transport.

and (with a slight abuse of terminology) denote the geodesic congruence obtained from it also by la . If v denotes the ..... Θ must be non-negative on E. The argument of the last paragraph now implies the second law of blackhole mechanics. ..... same; the horizon does not expand or contract. The null normal la to 2-spheres.

For scattering processes in which both s and t are significantly larger than the Planck mass we have string theory on the one hand, and on the other hand the physics of blackhole formation and decay. Both these descriptions are as yet ill understood. It is argued in this paper that a lot of insight

We briefly review the construction of multi-centered blackhole solutions in type IIA string theory. We then discuss a decoupling limit which embeds these solutions in M-theory on AdS(3) x S-2 x CY, and discuss some aspects of their dual CFT interpretation. Finally, we consider the quantization of

Full Text Available In this paper the low temperature zero-frequency transport in a 2+1-dimensional theory dual to a dyonic blackhole is discussed. It is shown that transport exhibits topological features: the transverse electric and heat conductivities satisfy the Wiedemann–Franz law of free electrons; the direct heat conductivity is measured in units of the central charge of CFT2+1, while the direct electric conductivity vanishes; the thermoelectric conductivity is non-zero at vanishing temperature, while the O(T behavior, controlled by the Mott relation, is subleading. Provided that the entropy of the blackhole, and the dual system, is non-vanishing at T=0, the observations indicate that the dyonic blackhole describes a ħ→0 limit of a highly degenerate topological state, in which the blackhole charge measures the density of excited non-abelian quasiparticles. The holographic description gives further evidence that non-abelian nature of quasiparticles can be determined by the low temperature behavior of the thermoelectric transport.

String propagation on a cone with deficit angle 2pi(1-1 / N) is considered for the purpose of computing the entropy of a large mass blackhole. The entropy computed using the recent results on condensation of twisted-sector tachyons in this theory is found to be in precise agreement with the Bekenstein-Hawking entropy.

We discuss isometric embedding diagrams for the visualization of initial data for the problem of the head-on collision of two blackholes. The problem of constructing the embedding diagrams is explicitly presented for the best studied initial data, the Misner geometry. We present a partial solution of the embedding diagrams and discuss issues related to completing the solution.

We propose a semiclassical method to calculate S-matrix elements for two-stage gravitational transitions involving matter collapse into a blackhole and evaporation of the latter. The method consistently incorporates back-reaction of the collapsing and emitted quanta on the metric. We illustrate the method in several toy models describing spherical self-gravitating shells in asymptotically flat and AdS space-times. We find that electrically neutral shells reflect via the above collapse-evaporation process with probability exp(-B), where B is the Bekenstein-Hawking entropy of the intermediate blackhole. This is consistent with interpretation of exp(B) as the number of blackhole states. The same expression for the probability is obtained in the case of charged shells if one takes into account instability of the Cauchy horizon of the intermediate Reissner-Nordstrom blackhole. Our semiclassical method opens a new systematic approach to the gravitational S-matrix in the non-perturbative regime.

The action of quantum fluctuations of the gravitational field may be regarded as the origin of the dissipative processes associated with Hawking radiation. In this picture the blackhole possesses internal coherence by virtue of the localization of its mass. The cumulative effect of the quantum fluctuations in the geometry is that this coherence is corrupted and the mass is sapped away. (author)

How can companies avoid corporate responsibility falling into a management black-hole? What can managers do to take corporate responsibility forward in their organisation, even if the company overall is indifferent or at an early stage of development in corporate responsibility?

We discuss the application of Siegel Modular Forms to BlackHole entropy counting. The role of the Igusa cusp form $\\chi_{10}$ in the D1D5P system is well-known, and its transformation properties are what allows precision microstate counting in this case. We apply a similar method to extract the

We propose a lower bound of the dc electrical conductivity in strongly disordered, strongly interacting quantum field theories using holography. We study linear response of blackholes with broken translational symmetry in Einstein–Maxwell-dilaton theories of gravity. Using the generalized Stokes equations at the horizon, we derive the lower bound of the electrical conductivity for the dual two dimensional disordered field theory.

In this letter, the effective-one-body Hamiltonian of two spinning blackhole considered and prequantization operators obtained by using the closed 2-form. It is indeed an application of prequantization method in a given physical system. Our results may be considered as mathematical tool and is useful to obtain the wave function.

Lovelock gravity consisting of the dimensionally continued Euler densities is a natural generalization of general relativity to higher dimensions such that equations of motion are still second order, and the theory is free of ghosts. A scalar field with a positive potential that yields an accelerating universe has been termed quintessence. We present exact blackhole solutions in D-dimensional Lovelock gravity surrounded by quintessence matter and also perform a detailed thermodynamical study. Further, we find that the mass, entropy and temperature of the blackhole are corrected due to the quintessence background. In particular, we find that a phase transition occurs with a divergence of the heat capacity at the critical horizon radius, and that specific heat becomes positive for r_hblack hole to become thermodynamically stable.

The first massive astrophysical blackholes likely formed at high redshifts (z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations. These blackholes grow by mergers and gas accretion, evolve into the population of bright quasars observed at lower redshifts, and eventually leave the supermassive blackhole remnants that are ubiquitous at the centers of galaxies in the nearby universe. The astrophysical processes responsible for the formation of the earliest seed blackholes...

A model for the formation of supermassive primordial blackholes in galactic nuclei with the simultaneous suppression of the formation of intermediate-mass blackholes is presented. A bimodal mass function for blackholes formed through phase transitions in a model with a "Mexican hat" potential has been found. The classical motion of the phase of a complex scalar field during inflation has been taken into account. Possible observational manifestations of primordial blackholes in galaxies an...

The general form of the action growth for a large class of static blackhole solutions in modified gravity which includes F (R ) -gravity models is computed. The cases of blackhole solutions with nonconstant Ricci scalar are also considered, generalizing the results previously found and valid only for blackholes with constant Ricci scalar. An argument is put forward to provide a physical interpretation of the results, which seem tightly connected with the generalized second law of blackhole thermodynamics.

Using the brick wall method, the entropy of the charged dilaton-axion blackhole is determined for both asymptotically flat and nonflat cases. The entropy turns out to be proportional to the horizon area of the blackhole confirming the Bekenstein-Hawking area-entropy formula for blackholes. The leading order logarithmic corrections to the entropy are also derived for such blackholes.

Blackhole spin will have a large impact on searches for gravitational waves with advanced detectors. While only a few stellar mass blackhole spins have been measured using X- ray techniques, gravitational wave detectors have the capacity to greatly increase the statistics of blackhole spin measurements. We show what we might learn from these measurements and how the blackhole spin values are influenced by their formation channels.

Binary blackholes occupy a special place in our quest for understanding the evolution of galaxies along cosmic history. If massive blackholes grow at the center of (pre-)galactic structures that experience a sequence of merger episodes, then dual blackholes form as inescapable outcome of galaxy assembly. But, if the blackholes reach coalescence, then they become the loudest sources of gravitational waves ever in the universe. Nature seems to provide a pathway for the formation of these ex...

Blackhole spin will have a large impact on searches for gravitational waves with advanced detectors. While only a few stellar mass blackhole spins have been measured using X- ray techniques, gravitational wave detectors have the capacity to greatly increase the statistics of blackhole spin measurements. We show what we might learn from these measurements and how the blackhole spin values are influenced by their formation channels. (paper)

In this paper, the Planck absolute entropy and the Bekenstein-Smarr formula of the rotating Banados-Teitelboim-Zanelli (BTZ) blackhole are presented via a complex thermodynamical system contributed by its inner and outer horizons. The redefined entropy approaches zero as the temperature of the rotating BTZ blackhole tends to absolute zero, satisfying the Nernst formulation of a blackhole. Hence, it can be regarded as the Planck absolute entropy of the rotating BTZ blackhole.

Doubly special relativity (DSR) is an effective model for encoding quantum gravity in flat spacetime. As result of the nonlinearity of the Lorentz transformation, the energy-momentum dispersion relation is modified. One simple way to import DSR to curved spacetime is ''Gravity's rainbow'', where the spacetime background felt by a test particle would depend on its energy. Focusing on the ''Amelino-Camelia dispersion relation'' which is E{sup 2} = m{sup 2}+p{sup 2}[1−η(E/m{sub p}){sup n}] with n > 0, we investigate the thermodynamical properties of a Schwarzschild blackhole and a static uncharged black string for all possible values of η and n in the framework of rainbow gravity. It shows that there are non-vanishing minimum masses for these two blackholes in the cases with η black hole, a Schwarzschild one and a static uncharged black string. It is found that the luminosities can be significantly suppressed or boosted depending on the values of η and n.

In this note, we derive (to third order in derivatives of the fluid velocity) a 2+1 dimensional theory of fluid dynamics that governs the evolution of generic long-wavelength perturbations of a black brane or large blackhole in four-dimensional gravity with negative cosmological constant, applying a systematic procedure developed recently by Bhattacharyya, Hubeny, Minwalla, and Rangamani. In the regime of validity of the fluid-dynamical description, the black-brane evolution will generically correspond to a turbulent flow. Turbulence in 2+1 dimensions has been well studied analytically, numerically, experimentally, and observationally as it provides a first approximation to the large scale dynamics of planetary atmospheres. These studies reveal dramatic differences between fluid flows in 2+1 and 3+1 dimensions, suggesting that the dynamics of perturbed four and five dimensional large AdS blackholes may be qualitatively different. However, further investigation is required to understand whether these qualitative differences exist in the regime of fluid dynamics relevant to blackhole dynamics.

We discuss static spherically symmetric metrics which represent nonsingular blackholes in four- and higher-dimensional spacetime. We impose a set of restrictions, such as a regularity of the metric at the center r =0 and Schwarzschild asymptotic behavior at large r . We assume that the metric besides mass M contains an additional parameter ℓ, which determines the scale where modification of the solution of the Einstein equations becomes significant. We require that the modified metric obeys the limiting curvature condition; that is, its curvature is uniformly restricted by the value ˜ℓ-2. We also make a "more technical" assumption that the metric coefficients are rational functions of r . In particular, the invariant (∇r )2 has the form Pn(r )/P˜n(r ), where Pn and P˜n are polynomials of the order of n . We discuss first the case of four dimensions. We show that when n ≤2 such a metric cannot describe a nonsingular blackhole. For n =3 we find a suitable metric, which besides M and ℓ contains a dimensionless numerical parameter. When this parameter vanishes, the obtained metric coincides with Hayward's one. The characteristic property of such spacetimes is -ξ2=(∇r )2, where ξ2 is a timelike at infinity Killing vector. We describe a possible generalization of a nonsingular black-hole metric to the case when this equality is violated. We also obtain a metric for a charged nonsingular blackhole obeying similar restrictions as the neutral one and construct higher dimensional models of neutral and charged blackholes.

We analyze the classical stability of Schwarzschild blackhole in massive conformal gravity which was recently proposed for another massive gravity model. This model in the Jordan frame is conformally equivalent to the Einstein–Weyl gravity in the Einstein frame. The coupled linearized Einstein equation is decomposed into the traceless and trace equation when one chooses 6m 2 φ=δR. Solving the traceless equation exhibits unstable modes featuring the Gregory–Laflamme s-mode instability of five-dimensional black string, while we find no unstable modes when solving the trace equation. It is shown that the instability of the blackhole in massive conformal gravity arises from the massiveness where the geometry of extra dimension trades for mass.

We present here an investigation of the event horizon of a charged blackhole embedded in a uniform magnetic field studying the Gaussian curvature. It is shown that the Gauss-Bonnet theorem holds for this magnetized blackhole and for a magnetized Kerr blackhole

The tight correlation between blackhole mass and velocity dispersion of galactic bulges is strong evidence that the formation of galaxies and supermassive blackholes are closely linked. I review the modeling of the joint formation of galaxies and their central supermassive blackholes in the context of the hierarchical structure formation paradigm.

Numerical simulations were performed for the formation process of rotating blackholes. It is suggested that Kerr blackholes are formed for wide ranges of initial parameters. The nature of gravitational waves from a test particle falling into a Kerr blackhole as well as the development of 3D numerical relativity for the coalescing binary neutron stars are discussed.

Jan 27, 2016 ... Abstract. The entropy spectrum of a modified Schwarzschild blackhole in the gravity's rainbow are investigated. By utilizing an action invariance of the blackhole with the help of Bohr–Sommerfield quantization rule, the entropy spectrum for the modified blackhole are calculated. The result of the equally ...

Abstract. We find a new rotating blackhole in three-dimensional anti-de Sitter space using an anisotropic perfect fluid inspired by the noncommutative blackhole. We deduce the thermodynam- ical quantities of this blackhole and compare them with those of a rotating BTZ solution and give corrections to the area law to get ...

We uncover two mechanisms that can render Kerr blackholes unstable in scalar-tensor gravity, both associated with the presence of matter in the vicinity of the blackhole and the fact that this introduces an effective mass for the scalar. Our results highlight the importance of understanding the structure of spacetime in realistic, astrophysical blackholes in scalar-tensor theories.

We ﬁnd a new rotating blackhole in three-dimensional anti-de Sitter space using an anisotropic perfect ﬂuid inspired by the noncommutative blackhole. We deduce the thermodynamical quantities of this blackhole and compare them with those of a rotating BTZ solution and give corrections to the area law to get the exact ...

The optical continuum luminosity and broad emission line width are often adopted to estimate the blackhole mass (virial blackhole mass). However, when the orientation of jets is close to the line of sight, jet emission would contribute significantly to the optical continuum. Therefore, the blackhole mass estimated by this ...

We look into the inner structure of a two-dimensional dilatonic evaporating blackhole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the blackhole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.

We look into the inner structure of a two-dimensional dilatonic evaporating blackhole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the blackhole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.

A brief overview is given of the theoretical underpinnings of the Membrane Paradigm for black-hole physics. Then those underpinnings are used to elucidate the Paradigm's view that the laws of black-hole thermodynamics (including the statistical origin of black-hole entropy) are just a special case of the laws of thermodynamics for an ordinary, rotating, thermal reservoir

This thesis contains a detailed study of various properties of supersymmetric blackholes. In chapter I an overview over some of the fascinating aspects of blackhole physics is provided. In particular, the string theory approach to blackhole entropy is discussed. One of the consequences of the